Merge branch 'master' into feature/naive

.travis.yml

@@ -4,6 +4,9 @@ go:
  - 1.2
  - release
  - tip
+before_install:
+ - sudo apt-get update -qq
+ - sudo apt-get install -qq libatlas-base-dev
 install:
  - go get github.com/smartystreets/goconvey/convey
- - go get -v ./...
+ - go get -v ./...

README.md

@@ -2,7 +2,8 @@ GoLearn
 =======
 
 <img src="http://talks.golang.org/2013/advconc/gopherhat.jpg" width=125><br>
-[![GoDoc](https://godoc.org/github.com/sjwhitworth/golearn?status.png)](https://godoc.org/github.com/sjwhitworth/golearn)<br>
+[![GoDoc](https://godoc.org/github.com/sjwhitworth/golearn?status.png)](https://godoc.org/github.com/sjwhitworth/golearn)
+[![Build Status](https://travis-ci.org/sjwhitworth/golearn.png?branch=master)](https://travis-ci.org/sjwhitworth/golearn)<br>
 
 GoLearn is a 'batteries included' machine learning library for Go. **Simplicity**, paired with customisability, is the goal.
 We are in active development, and would love comments from users out in the wild. Drop us a line on Twitter.

base/attributes.go

@@ -219,7 +219,7 @@ func (Attr *CategoricalAttribute) GetSysValFromString(rawVal string) float64 {
 // Returns a string containing the list of human-readable values this
 // CategoricalAttribute can take.
 func (Attr *CategoricalAttribute) String() string {
-	return fmt.Sprintf("CategoricalAttribute(%s)", Attr.values)
+	return fmt.Sprintf("CategoricalAttribute(\"%s\", %s)", Attr.Name, Attr.values)
 }
 
 // GetStringFromSysVal returns a human-readable value from the given system-representation

base/instances.go

@@ -5,8 +5,9 @@ import (
 	"encoding/binary"
 	"errors"
 	"fmt"
-	"github.com/gonum/matrix/mat64"
 	"math/rand"
+
+	"github.com/gonum/matrix/mat64"
 )
 
 // SortDirection specifies sorting direction...
@@ -171,10 +172,11 @@ func NewInstancesFromDense(attrs []Attribute, rows int, mat *mat64.Dense) *Insta
 //
 // IMPORTANT: this function is only meaningful when prop is between 0.0 and 1.0.
 // Using any other values may result in odd behaviour.
-func InstancesTrainTestSplit(src *Instances, prop float64) [2](*Instances) {
+func InstancesTrainTestSplit(src *Instances, prop float64) (*Instances, *Instances) {
 	trainingRows := make([]int, 0)
 	testingRows := make([]int, 0)
 	numAttrs := len(src.attributes)
+	src.Shuffle()
 	for i := 0; i < src.Rows; i++ {
 		trainOrTest := rand.Intn(101)
 		if trainOrTest > int(100*prop) {
@@ -196,10 +198,10 @@ func InstancesTrainTestSplit(src *Instances, prop float64) [2](*Instances) {
 		rawTestMatrix.SetRow(i, rowDat)
 	}
 
-	var ret [2]*Instances
-	ret[0] = NewInstancesFromDense(src.attributes, len(trainingRows), rawTrainMatrix)
-	ret[1] = NewInstancesFromDense(src.attributes, len(testingRows), rawTestMatrix)
-	return ret
+
+	trainingRet := NewInstancesFromDense(src.attributes, len(trainingRows), rawTrainMatrix)
+	testRet := NewInstancesFromDense(src.attributes, len(testingRows), rawTestMatrix)
+	return trainingRet, testRet
 }
 
 // CountAttrValues returns the distribution of values of a given
@@ -273,6 +275,33 @@ func (inst *Instances) DecomposeOnAttributeValues(at Attribute) map[string]*Inst
 	return ret
 }
 
+func (inst *Instances) GetClassDistributionAfterSplit(at Attribute) map[string]map[string]int {
+
+	ret := make(map[string]map[string]int)
+
+	// Find the attribute we're decomposing on
+	attrIndex := inst.GetAttrIndex(at)
+	if attrIndex == -1 {
+		panic("Invalid attribute index")
+	}
+
+	// Get the class index
+	classAttr := inst.GetAttr(inst.ClassIndex)
+
+	for i := 0; i < inst.Rows; i++ {
+		splitVar := at.GetStringFromSysVal(inst.Get(i, attrIndex))
+		classVar := classAttr.GetStringFromSysVal(inst.Get(i, inst.ClassIndex))
+		if _, ok := ret[splitVar]; !ok {
+			ret[splitVar] = make(map[string]int)
+			i--
+			continue
+		}
+		ret[splitVar][classVar]++
+	}
+
+	return ret
+}
+
 // Get returns the system representation (float64) of the value
 // stored at the given row and col coordinate.
 func (inst *Instances) Get(row int, col int) float64 {
@@ -308,6 +337,20 @@ func (inst *Instances) GetClass(row int) string {
 	return attr.GetStringFromSysVal(val)
 }
 
+// GetClassDist returns a map containing the count of each
+// class type (indexed by the class' string representation)
+func (inst *Instances) GetClassDistribution() map[string]int {
+	ret := make(map[string]int)
+	attr := inst.GetAttr(inst.ClassIndex)
+	for i := 0; i < inst.Rows; i++ {
+		val := inst.Get(i, inst.ClassIndex)
+		cls := attr.GetStringFromSysVal(val)
+		ret[cls]++
+	}
+
+	return ret
+}
+
 func (Inst *Instances) GetClassAttrPtr() *Attribute {
 	attr := Inst.GetAttr(Inst.ClassIndex)
 	return &attr
@@ -465,7 +508,7 @@ func (inst *Instances) GeneratePredictionVector() *Instances {
 // Shuffle randomizes the row order in place
 func (inst *Instances) Shuffle() {
 	for i := 0; i < inst.Rows; i++ {
-		j := rand.Intn(inst.Rows)
+		j := rand.Intn(i + 1)
 		inst.swapRows(i, j)
 	}
 }

ensemble/ensemble.go

@@ -0,0 +1,13 @@
+/*
+
+	Ensemble contains classifiers which combine other classifiers.
+
+	RandomForest:
+		Generates ForestSize bagged decision trees (currently ID3-based)
+			each considering a fixed number of random features.
+
+		Built on meta.Bagging
+
+*/
+
+package ensemble

ensemble/randomforest.go

@@ -0,0 +1,50 @@
+package ensemble
+
+import (
+	base "github.com/sjwhitworth/golearn/base"
+	meta "github.com/sjwhitworth/golearn/meta"
+	trees "github.com/sjwhitworth/golearn/trees"
+	"fmt"
+)
+
+// RandomForest classifies instances using an ensemble
+// of bagged random decision trees
+type RandomForest struct {
+	base.BaseClassifier
+	ForestSize int
+	Features   int
+	Model      *meta.BaggedModel
+}
+
+// NewRandomForests generates and return a new random forests
+// forestSize controls the number of trees that get built
+// features controls the number of features used to build each tree
+func NewRandomForest(forestSize int, features int) *RandomForest {
+	ret := &RandomForest{
+		base.BaseClassifier{},
+		forestSize,
+		features,
+		nil,
+	}
+	return ret
+}
+
+// Train builds the RandomForest on the specified instances
+func (f *RandomForest) Fit(on *base.Instances) {
+	f.Model = new(meta.BaggedModel)
+	f.Model.RandomFeatures = f.Features
+	for i := 0; i < f.ForestSize; i++ {
+		tree := trees.NewID3DecisionTree(0.00)
+		f.Model.AddModel(tree)
+	}
+	f.Model.Fit(on)
+}
+
+// Predict generates predictions from a trained RandomForest
+func (f *RandomForest) Predict(with *base.Instances) *base.Instances {
+	return f.Model.Predict(with)
+}
+
+func (f *RandomForest) String() string {
+	return fmt.Sprintf("RandomForest(ForestSize: %d, Features:%d, %s\n)", f.ForestSize, f.Features, f.Model)
+}

ensemble/randomforest_test.go

@@ -0,0 +1,29 @@
+package ensemble
+
+import (
+	"fmt"
+	base "github.com/sjwhitworth/golearn/base"
+	eval "github.com/sjwhitworth/golearn/evaluation"
+	filters "github.com/sjwhitworth/golearn/filters"
+	"testing"
+)
+
+func TestRandomForest1(testEnv *testing.T) {
+	inst, err := base.ParseCSVToInstances("../examples/datasets/iris_headers.csv", true)
+	if err != nil {
+		panic(err)
+	}
+	trainData, testData := base.InstancesTrainTestSplit(inst, 0.60)
+	filt := filters.NewChiMergeFilter(trainData, 0.90)
+	filt.AddAllNumericAttributes()
+	filt.Build()
+	filt.Run(testData)
+	filt.Run(trainData)
+	rf := NewRandomForest(10, 3)
+	rf.Fit(trainData)
+	predictions := rf.Predict(testData)
+	fmt.Println(predictions)
+	confusionMat := eval.GetConfusionMatrix(testData, predictions)
+	fmt.Println(confusionMat)
+	fmt.Println(eval.GetSummary(confusionMat))
+}

examples/datasets/tennis.csv

@@ -0,0 +1,15 @@
+outlook,temp,humidity,windy,play
+sunny,hot,high,false,no
+sunny,hot,high,true,no
+overcast,hot,high,false,yes
+rainy,mild,high,false,yes
+rainy,cool,normal,false,yes
+rainy,cool,normal,true,no
+overcast,cool,normal,true,yes
+sunny,mild,high,false,no
+sunny,cool,normal,false,yes
+rainy,mild,normal,false,yes
+sunny,mild,normal,true,yes
+overcast,mild,high,true,yes
+overcast,hot,normal,false,yes
+rainy,mild,high,true,no

examples/knnclassifier/knnclassifier_iris.go

@@ -17,9 +17,7 @@ func main() {
 	cls := knn.NewKnnClassifier("euclidean", 2)
 
 	//Do a training-test split
-	trainTest := base.InstancesTrainTestSplit(rawData, 0.50)
-	trainData := trainTest[0]
-	testData := trainTest[1]
+	trainData, testData := base.InstancesTrainTestSplit(rawData, 0.50)
 	cls.Fit(trainData)
 
 	//Calculates the Euclidean distance and returns the most popular label

examples/trees/trees.go

@@ -0,0 +1,75 @@
+// Demonstrates decision tree classification
+
+package main
+
+import (
+	"fmt"
+	base "github.com/sjwhitworth/golearn/base"
+	eval "github.com/sjwhitworth/golearn/evaluation"
+	filters "github.com/sjwhitworth/golearn/filters"
+	ensemble "github.com/sjwhitworth/golearn/ensemble"
+	trees "github.com/sjwhitworth/golearn/trees"
+	"math/rand"
+	"time"
+)
+
+func main () {
+
+	var tree base.Classifier
+
+	rand.Seed(time.Now().UTC().UnixNano())
+
+	// Load in the iris dataset
+	iris, err := base.ParseCSVToInstances("../datasets/iris_headers.csv", true)
+	if err != nil {
+		panic(err)
+	}
+
+	// Discretise the iris dataset with Chi-Merge
+	filt := filters.NewChiMergeFilter(iris, 0.99)
+	filt.AddAllNumericAttributes()
+	filt.Build()
+	filt.Run(iris)
+
+	// Create a 60-40 training-test split
+	trainData, testData := base.InstancesTrainTestSplit(iris, 0.60)
+
+	//
+	// First up, use ID3
+	//
+	tree = trees.NewID3DecisionTree(0.6)
+	// (Parameter controls train-prune split.)
+
+	// Train the ID3 tree
+	tree.Fit(trainData)
+
+	// Generate predictions
+	predictions := tree.Predict(testData)
+
+	// Evaluate
+	fmt.Println("ID3 Performance")
+	cf := eval.GetConfusionMatrix(testData, predictions)
+	fmt.Println(eval.GetSummary(cf))
+
+	//
+	// Next up, Random Trees
+	//
+
+	// Consider two randomly-chosen attributes
+	tree = trees.NewRandomTree(2)
+	tree.Fit(testData)
+	predictions = tree.Predict(testData)
+	fmt.Println("RandomTree Performance")
+	cf = eval.GetConfusionMatrix(testData, predictions)
+	fmt.Println(eval.GetSummary(cf))
+
+	//
+	// Finally, Random Forests
+	//
+	tree = ensemble.NewRandomForest(100, 3)
+	tree.Fit(trainData)
+	predictions = tree.Predict(testData)
+	fmt.Println("RandomForest Performance")
+	cf = eval.GetConfusionMatrix(testData, predictions)
+	fmt.Println(eval.GetSummary(cf))
+}

filters/chimerge.go

@@ -43,6 +43,21 @@ func (c *ChiMergeFilter) Build() {
 	}
 }
 
+// AddAllNumericAttributes adds every suitable attribute
+// to the ChiMergeFilter for discretisation
+func (b *ChiMergeFilter) AddAllNumericAttributes() {
+	for i := 0; i < b.Instances.Cols; i++ {
+		if i == b.Instances.ClassIndex {
+			continue
+		}
+		attr := b.Instances.GetAttr(i)
+		if attr.GetType() != base.Float64Type {
+			continue
+		}
+		b.Attributes = append(b.Attributes, i)
+	}
+}
+
 // Run discretises the set of Instances `on'
 //
 // IMPORTANT: ChiMergeFilter discretises in place.

meta/bagging.go

@@ -0,0 +1,190 @@
+package meta
+
+import (
+	"fmt"
+	base "github.com/sjwhitworth/golearn/base"
+	"math/rand"
+	"runtime"
+	"strings"
+	"sync"
+)
+
+// BaggedModel trains base.Classifiers on subsets of the original
+// Instances and combine the results through voting
+type BaggedModel struct {
+	base.BaseClassifier
+	Models             []base.Classifier
+	RandomFeatures     int
+	lock               sync.Mutex
+	selectedAttributes map[int][]base.Attribute
+}
+
+// generateTrainingAttrs selects RandomFeatures number of base.Attributes from
+// the provided base.Instances.
+func (b *BaggedModel) generateTrainingAttrs(model int, from *base.Instances) []base.Attribute {
+	ret := make([]base.Attribute, 0)
+	if b.RandomFeatures == 0 {
+		for j := 0; j < from.Cols; j++ {
+			attr := from.GetAttr(j)
+			ret = append(ret, attr)
+		}
+	} else {
+		for {
+			if len(ret) >= b.RandomFeatures {
+				break
+			}
+			attrIndex := rand.Intn(from.Cols)
+			if attrIndex == from.ClassIndex {
+				continue
+			}
+			attr := from.GetAttr(attrIndex)
+			matched := false
+			for _, a := range ret {
+				if a.Equals(attr) {
+					matched = true
+					break
+				}
+			}
+			if !matched {
+				ret = append(ret, attr)
+			}
+		}
+	}
+	ret = append(ret, from.GetClassAttr())
+	b.lock.Lock()
+	b.selectedAttributes[model] = ret
+	b.lock.Unlock()
+	return ret
+}
+
+// generatePredictionInstances returns a modified version of the
+// requested base.Instances with only the base.Attributes selected
+// for training the model.
+func (b *BaggedModel) generatePredictionInstances(model int, from *base.Instances) *base.Instances {
+	selected := b.selectedAttributes[model]
+	return from.SelectAttributes(selected)
+}
+
+// generateTrainingInstances generates RandomFeatures number of
+// attributes and returns a modified version of base.Instances
+// for training the model
+func (b *BaggedModel) generateTrainingInstances(model int, from *base.Instances) *base.Instances {
+	insts := from.SampleWithReplacement(from.Rows)
+	selected := b.generateTrainingAttrs(model, from)
+	return insts.SelectAttributes(selected)
+}
+
+// AddModel adds a base.Classifier to the current model
+func (b *BaggedModel) AddModel(m base.Classifier) {
+	b.Models = append(b.Models, m)
+}
+
+// Train generates and trains each model on a randomised subset of
+// Instances.
+func (b *BaggedModel) Fit(from *base.Instances) {
+	var wait sync.WaitGroup
+	b.selectedAttributes = make(map[int][]base.Attribute)
+	for i, m := range b.Models {
+		wait.Add(1)
+		go func(c base.Classifier, f *base.Instances, model int) {
+			l := b.generateTrainingInstances(model, f)
+			c.Fit(l)
+			wait.Done()
+		}(m, from, i)
+	}
+	wait.Wait()
+}
+
+// Predict gathers predictions from all the classifiers
+// and outputs the most common (majority) class
+//
+// IMPORTANT: in the event of a tie, the first class which
+// achieved the tie value is output.
+func (b *BaggedModel) Predict(from *base.Instances) *base.Instances {
+	n := runtime.NumCPU()
+	// Channel to receive the results as they come in
+	votes := make(chan *base.Instances, n)
+	// Count the votes for each class
+	voting := make(map[int](map[string]int))
+
+	// Create a goroutine to collect the votes
+	var votingwait sync.WaitGroup
+	votingwait.Add(1)
+	go func() {
+		for {
+			incoming, ok := <-votes
+			if ok {
+				// Step through each prediction
+				for j := 0; j < incoming.Rows; j++ {
+					// Check if we've seen this class before...
+					if _, ok := voting[j]; !ok {
+						// If we haven't, create an entry
+						voting[j] = make(map[string]int)
+						// Continue on the current row
+						j--
+						continue
+					}
+					voting[j][incoming.GetClass(j)]++
+				}
+			} else {
+				votingwait.Done()
+				break
+			}
+		}
+	}()
+
+	// Create workers to process the predictions
+	processpipe := make(chan int, n)
+	var processwait sync.WaitGroup
+	for i := 0; i < n; i++ {
+		processwait.Add(1)
+		go func() {
+			for {
+				if i, ok := <-processpipe; ok {
+					c := b.Models[i]
+					l := b.generatePredictionInstances(i, from)
+					votes <- c.Predict(l)
+				} else {
+					processwait.Done()
+					break
+				}
+			}
+		}()
+	}
+
+	// Send all the models to the workers for prediction
+	for i, _ := range b.Models {
+		processpipe <- i
+	}
+	close(processpipe) // Finished sending models to be predicted
+	processwait.Wait() // Predictors all finished processing
+	close(votes)       // Close the vote channel and allow it to drain
+	votingwait.Wait()  // All the votes are in
+
+	// Generate the overall consensus
+	ret := from.GeneratePredictionVector()
+	for i := range voting {
+		maxClass := ""
+		maxCount := 0
+		// Find the most popular class
+		for c := range voting[i] {
+			votes := voting[i][c]
+			if votes > maxCount {
+				maxClass = c
+				maxCount = votes
+			}
+		}
+		ret.SetAttrStr(i, 0, maxClass)
+	}
+	return ret
+}
+
+// String returns a human-readable representation of the
+// BaggedModel and everything it contains
+func (b *BaggedModel) String() string {
+	children := make([]string, 0)
+	for i, m := range b.Models {
+		children = append(children, fmt.Sprintf("%d: %s", i, m))
+	}
+	return fmt.Sprintf("BaggedModel(\n%s)", strings.Join(children, "\n\t"))
+}

meta/bagging_test.go

@@ -0,0 +1,83 @@
+package meta
+
+import (
+	"fmt"
+	base "github.com/sjwhitworth/golearn/base"
+	eval "github.com/sjwhitworth/golearn/evaluation"
+	filters "github.com/sjwhitworth/golearn/filters"
+	trees "github.com/sjwhitworth/golearn/trees"
+	"math/rand"
+	"testing"
+	"time"
+)
+
+func BenchmarkBaggingRandomForestFit(testEnv *testing.B) {
+	inst, err := base.ParseCSVToInstances("../examples/datasets/iris_headers.csv", true)
+	if err != nil {
+		panic(err)
+	}
+
+	rand.Seed(time.Now().UnixNano())
+	filt := filters.NewChiMergeFilter(inst, 0.90)
+	filt.AddAllNumericAttributes()
+	filt.Build()
+	filt.Run(inst)
+	rf := new(BaggedModel)
+	for i := 0; i < 10; i++ {
+		rf.AddModel(trees.NewRandomTree(2))
+	}
+	testEnv.ResetTimer()
+	for i := 0; i < 20; i++ {
+		rf.Fit(inst)
+	}
+}
+
+func BenchmarkBaggingRandomForestPredict(testEnv *testing.B) {
+	inst, err := base.ParseCSVToInstances("../examples/datasets/iris_headers.csv", true)
+	if err != nil {
+		panic(err)
+	}
+
+	rand.Seed(time.Now().UnixNano())
+	filt := filters.NewChiMergeFilter(inst, 0.90)
+	filt.AddAllNumericAttributes()
+	filt.Build()
+	filt.Run(inst)
+	rf := new(BaggedModel)
+	for i := 0; i < 10; i++ {
+		rf.AddModel(trees.NewRandomTree(2))
+	}
+	rf.Fit(inst)
+	testEnv.ResetTimer()
+	for i := 0; i < 20; i++ {
+		rf.Predict(inst)
+	}
+}
+
+func TestRandomForest1(testEnv *testing.T) {
+	inst, err := base.ParseCSVToInstances("../examples/datasets/iris_headers.csv", true)
+	if err != nil {
+		panic(err)
+	}
+
+	rand.Seed(time.Now().UnixNano())
+	trainData, testData := base.InstancesTrainTestSplit(inst, 0.6)
+	filt := filters.NewChiMergeFilter(inst, 0.90)
+	filt.AddAllNumericAttributes()
+	filt.Build()
+	filt.Run(testData)
+	filt.Run(trainData)
+	rf := new(BaggedModel)
+	for i := 0; i < 10; i++ {
+		rf.AddModel(trees.NewRandomTree(2))
+	}
+	rf.Fit(trainData)
+	fmt.Println(rf)
+	predictions := rf.Predict(testData)
+	fmt.Println(predictions)
+	confusionMat := eval.GetConfusionMatrix(testData, predictions)
+	fmt.Println(confusionMat)
+	fmt.Println(eval.GetMacroPrecision(confusionMat))
+	fmt.Println(eval.GetMacroRecall(confusionMat))
+	fmt.Println(eval.GetSummary(confusionMat))
+}

trees/decision_trees.go

@@ -1,12 +0,0 @@
-package trees
-
-import base "github.com/sjwhitworth/golearn/base"
-
-type DecisionTree struct {
-	base.BaseEstimator
-}
-
-type Branch struct {
-	LeftBranch  Branch
-	RightBranch Branch
-}

trees/entropy.go

@@ -0,0 +1,100 @@
+package trees
+
+import (
+	base "github.com/sjwhitworth/golearn/base"
+	"math"
+)
+
+//
+// Information gain rule generator
+//
+
+type InformationGainRuleGenerator struct {
+}
+
+// GetSplitAttribute returns the non-class Attribute which maximises the
+// information gain.
+//
+// IMPORTANT: passing a base.Instances with no Attributes other than the class
+// variable will panic()
+func (r *InformationGainRuleGenerator) GenerateSplitAttribute(f *base.Instances) base.Attribute {
+	allAttributes := make([]int, 0)
+	for i := 0; i < f.Cols; i++ {
+		if i != f.ClassIndex {
+			allAttributes = append(allAttributes, i)
+		}
+	}
+	return r.GetSplitAttributeFromSelection(allAttributes, f)
+}
+
+// GetSplitAttribute from selection returns the class Attribute which maximises
+// the information gain amongst consideredAttributes
+//
+// IMPORTANT: passing a zero-length consideredAttributes parameter will panic()
+func (r *InformationGainRuleGenerator) GetSplitAttributeFromSelection(consideredAttributes []int, f *base.Instances) base.Attribute {
+
+	// Next step is to compute the information gain at this node
+	// for each randomly chosen attribute, and pick the one
+	// which maximises it
+	maxGain := math.Inf(-1)
+	selectedAttribute := -1
+
+	// Compute the base entropy
+	classDist := f.GetClassDistribution()
+	baseEntropy := getBaseEntropy(classDist)
+
+	// Compute the information gain for each attribute
+	for _, s := range consideredAttributes {
+		proposedClassDist := f.GetClassDistributionAfterSplit(f.GetAttr(s))
+		localEntropy := getSplitEntropy(proposedClassDist)
+		informationGain := baseEntropy - localEntropy
+		if informationGain > maxGain {
+			maxGain = informationGain
+			selectedAttribute = s
+		}
+	}
+
+	// Pick the one which maximises IG
+	return f.GetAttr(selectedAttribute)
+}
+
+//
+// Entropy functions
+//
+
+// getSplitEntropy determines the entropy of the target
+// class distribution after splitting on an base.Attribute
+func getSplitEntropy(s map[string]map[string]int) float64 {
+	ret := 0.0
+	count := 0
+	for a := range s {
+		for c := range s[a] {
+			count += s[a][c]
+		}
+	}
+	for a := range s {
+		total := 0.0
+		for c := range s[a] {
+			total += float64(s[a][c])
+		}
+		for c := range s[a] {
+			ret -= float64(s[a][c]) / float64(count) * math.Log(float64(s[a][c])/float64(count)) / math.Log(2)
+		}
+		ret += total / float64(count) * math.Log(total/float64(count)) / math.Log(2)
+	}
+	return ret
+}
+
+// getBaseEntropy determines the entropy of the target
+// class distribution before splitting on an base.Attribute
+func getBaseEntropy(s map[string]int) float64 {
+	ret := 0.0
+	count := 0
+	for k := range s {
+		count += s[k]
+	}
+	for k := range s {
+		ret -= float64(s[k]) / float64(count) * math.Log(float64(s[k])/float64(count)) / math.Log(2)
+	}
+	return ret
+}

trees/id3.go

@@ -0,0 +1,267 @@
+package trees
+
+import (
+	"bytes"
+	"fmt"
+	base "github.com/sjwhitworth/golearn/base"
+	eval "github.com/sjwhitworth/golearn/evaluation"
+	"sort"
+)
+
+// NodeType determines whether a DecisionTreeNode is a leaf or not
+type NodeType int
+
+const (
+	// LeafNode means there are no children
+	LeafNode NodeType = 1
+	// RuleNode means we should look at the next attribute value
+	RuleNode NodeType = 2
+)
+
+// RuleGenerator implementations analyse instances and determine
+// the best value to split on
+type RuleGenerator interface {
+	GenerateSplitAttribute(*base.Instances) base.Attribute
+}
+
+// DecisionTreeNode represents a given portion of a decision tree
+type DecisionTreeNode struct {
+	Type      NodeType
+	Children  map[string]*DecisionTreeNode
+	SplitAttr base.Attribute
+	ClassDist map[string]int
+	Class     string
+	ClassAttr *base.Attribute
+}
+
+// InferID3Tree builds a decision tree using a RuleGenerator
+// from a set of Instances (implements the ID3 algorithm)
+func InferID3Tree(from *base.Instances, with RuleGenerator) *DecisionTreeNode {
+	// Count the number of classes at this node
+	classes := from.CountClassValues()
+	// If there's only one class, return a DecisionTreeLeaf with
+	// the only class available
+	if len(classes) == 1 {
+		maxClass := ""
+		for i := range classes {
+			maxClass = i
+		}
+		ret := &DecisionTreeNode{
+			LeafNode,
+			nil,
+			nil,
+			classes,
+			maxClass,
+			from.GetClassAttrPtr(),
+		}
+		return ret
+	}
+
+	// Only have the class attribute
+	maxVal := 0
+	maxClass := ""
+	for i := range classes {
+		if classes[i] > maxVal {
+			maxClass = i
+			maxVal = classes[i]
+		}
+	}
+
+	// If there are no more Attributes left to split on,
+	// return a DecisionTreeLeaf with the majority class
+	if from.GetAttributeCount() == 2 {
+		ret := &DecisionTreeNode{
+			LeafNode,
+			nil,
+			nil,
+			classes,
+			maxClass,
+			from.GetClassAttrPtr(),
+		}
+		return ret
+	}
+
+	ret := &DecisionTreeNode{
+		RuleNode,
+		nil,
+		nil,
+		classes,
+		maxClass,
+		from.GetClassAttrPtr(),
+	}
+
+	// Generate a return structure
+	// Generate the splitting attribute
+	splitOnAttribute := with.GenerateSplitAttribute(from)
+	if splitOnAttribute == nil {
+		// Can't determine, just return what we have
+		return ret
+	}
+	// Split the attributes based on this attribute's value
+	splitInstances := from.DecomposeOnAttributeValues(splitOnAttribute)
+	// Create new children from these attributes
+	ret.Children = make(map[string]*DecisionTreeNode)
+	for k := range splitInstances {
+		newInstances := splitInstances[k]
+		ret.Children[k] = InferID3Tree(newInstances, with)
+	}
+	ret.SplitAttr = splitOnAttribute
+	return ret
+}
+
+// getNestedString returns the contents of node d
+// prefixed by level number of tags (also prints children)
+func (d *DecisionTreeNode) getNestedString(level int) string {
+	buf := bytes.NewBuffer(nil)
+	tmp := bytes.NewBuffer(nil)
+	for i := 0; i < level; i++ {
+		tmp.WriteString("\t")
+	}
+	buf.WriteString(tmp.String())
+	if d.Children == nil {
+		buf.WriteString(fmt.Sprintf("Leaf(%s)", d.Class))
+	} else {
+		buf.WriteString(fmt.Sprintf("Rule(%s)", d.SplitAttr.GetName()))
+		keys := make([]string, 0)
+		for k := range d.Children {
+			keys = append(keys, k)
+		}
+		sort.Strings(keys)
+		for _, k := range keys {
+			buf.WriteString("\n")
+			buf.WriteString(tmp.String())
+			buf.WriteString("\t")
+			buf.WriteString(k)
+			buf.WriteString("\n")
+			buf.WriteString(d.Children[k].getNestedString(level + 1))
+		}
+	}
+	return buf.String()
+}
+
+// String returns a human-readable representation of a given node
+// and it's children
+func (d *DecisionTreeNode) String() string {
+	return d.getNestedString(0)
+}
+
+// computeAccuracy is a helper method for Prune()
+func computeAccuracy(predictions *base.Instances, from *base.Instances) float64 {
+	cf := eval.GetConfusionMatrix(from, predictions)
+	return eval.GetAccuracy(cf)
+}
+
+// Prune eliminates branches which hurt accuracy
+func (d *DecisionTreeNode) Prune(using *base.Instances) {
+	// If you're a leaf, you're already pruned
+	if d.Children == nil {
+		return
+	} else {
+		if d.SplitAttr == nil {
+			return
+		}
+		// Recursively prune children of this node
+		sub := using.DecomposeOnAttributeValues(d.SplitAttr)
+		for k := range d.Children {
+			if sub[k] == nil {
+				continue
+			}
+			d.Children[k].Prune(sub[k])
+		}
+	}
+
+	// Get a baseline accuracy
+	baselineAccuracy := computeAccuracy(d.Predict(using), using)
+
+	// Speculatively remove the children and re-evaluate
+	tmpChildren := d.Children
+	d.Children = nil
+	newAccuracy := computeAccuracy(d.Predict(using), using)
+
+	// Keep the children removed if better, else restore
+	if newAccuracy < baselineAccuracy {
+		d.Children = tmpChildren
+	}
+}
+
+// Predict outputs a base.Instances containing predictions from this tree
+func (d *DecisionTreeNode) Predict(what *base.Instances) *base.Instances {
+	outputAttrs := make([]base.Attribute, 1)
+	outputAttrs[0] = what.GetClassAttr()
+	predictions := base.NewInstances(outputAttrs, what.Rows)
+	for i := 0; i < what.Rows; i++ {
+		cur := d
+		for {
+			if cur.Children == nil {
+				predictions.SetAttrStr(i, 0, cur.Class)
+				break
+			} else {
+				at := cur.SplitAttr
+				j := what.GetAttrIndex(at)
+				if j == -1 {
+					predictions.SetAttrStr(i, 0, cur.Class)
+					break
+				}
+				classVar := at.GetStringFromSysVal(what.Get(i, j))
+				if next, ok := cur.Children[classVar]; ok {
+					cur = next
+				} else {
+					var bestChild string
+					for c := range cur.Children {
+						bestChild = c
+						if c > classVar {
+							break
+						}
+					}
+					cur = cur.Children[bestChild]
+				}
+			}
+		}
+	}
+	return predictions
+}
+
+//
+// ID3 Tree type
+//
+
+// ID3DecisionTree represents an ID3-based decision tree
+// using the Information Gain metric to select which attributes
+// to split on at each node.
+type ID3DecisionTree struct {
+	base.BaseClassifier
+	Root       *DecisionTreeNode
+	PruneSplit float64
+}
+
+// Returns a new ID3DecisionTree with the specified test-prune
+// ratio. Of the ratio is less than 0.001, the tree isn't pruned
+func NewID3DecisionTree(prune float64) *ID3DecisionTree {
+	return &ID3DecisionTree{
+		base.BaseClassifier{},
+		nil,
+		prune,
+	}
+}
+
+// Fit builds the ID3 decision tree
+func (t *ID3DecisionTree) Fit(on *base.Instances) {
+	rule := new(InformationGainRuleGenerator)
+	if t.PruneSplit > 0.001 {
+		trainData, testData := base.InstancesTrainTestSplit(on, t.PruneSplit)
+		t.Root = InferID3Tree(trainData, rule)
+		t.Root.Prune(testData)
+	} else {
+		t.Root = InferID3Tree(on, rule)
+	}
+}
+
+// Predict outputs predictions from the ID3 decision tree
+func (t *ID3DecisionTree) Predict(what *base.Instances) *base.Instances {
+	return t.Root.Predict(what)
+}
+
+// String returns a human-readable version of this ID3 tree
+func (t *ID3DecisionTree) String() string {
+	return fmt.Sprintf("ID3DecisionTree(%s\n)", t.Root)
+}

trees/random.go

@@ -0,0 +1,88 @@
+package trees
+
+import (
+	"fmt"
+	base "github.com/sjwhitworth/golearn/base"
+	"math/rand"
+)
+
+// RandomTreeRuleGenerator is used to generate decision rules for Random Trees
+type RandomTreeRuleGenerator struct {
+	Attributes   int
+	internalRule InformationGainRuleGenerator
+}
+
+// GenerateSplitAttribute returns the best attribute out of those randomly chosen
+// which maximises Information Gain
+func (r *RandomTreeRuleGenerator) GenerateSplitAttribute(f *base.Instances) base.Attribute {
+
+	// First step is to generate the random attributes that we'll consider
+	maximumAttribute := f.GetAttributeCount()
+	consideredAttributes := make([]int, r.Attributes)
+	attrCounter := 0
+	for {
+		if len(consideredAttributes) >= r.Attributes {
+			break
+		}
+		selectedAttribute := rand.Intn(maximumAttribute)
+		fmt.Println(selectedAttribute, attrCounter, consideredAttributes, len(consideredAttributes))
+		if selectedAttribute != f.ClassIndex {
+			matched := false
+			for _, a := range consideredAttributes {
+				if a == selectedAttribute {
+					matched = true
+					break
+				}
+			}
+			if matched {
+				continue
+			}
+			consideredAttributes = append(consideredAttributes, selectedAttribute)
+			attrCounter++
+		}
+	}
+
+	return r.internalRule.GetSplitAttributeFromSelection(consideredAttributes, f)
+}
+
+// RandomTree builds a decision tree by considering a fixed number
+// of randomly-chosen attributes at each node
+type RandomTree struct {
+	base.BaseClassifier
+	Root *DecisionTreeNode
+	Rule *RandomTreeRuleGenerator
+}
+
+// NewRandomTree returns a new RandomTree which considers attrs randomly
+// chosen attributes at each node.
+func NewRandomTree(attrs int) *RandomTree {
+	return &RandomTree{
+		base.BaseClassifier{},
+		nil,
+		&RandomTreeRuleGenerator{
+			attrs,
+			InformationGainRuleGenerator{},
+		},
+	}
+}
+
+// Train builds a RandomTree suitable for prediction
+func (rt *RandomTree) Fit(from *base.Instances) {
+	rt.Root = InferID3Tree(from, rt.Rule)
+}
+
+// Predict returns a set of Instances containing predictions
+func (rt *RandomTree) Predict(from *base.Instances) *base.Instances {
+	return rt.Root.Predict(from)
+}
+
+// String returns a human-readable representation of this structure
+func (rt *RandomTree) String() string {
+	return fmt.Sprintf("RandomTree(%s)", rt.Root)
+}
+
+// Prune removes nodes from the tree which are detrimental
+// to determining the accuracy of the test set (with)
+func (rt *RandomTree) Prune(with *base.Instances) {
+	rt.Root.Prune(with)
+}

trees/tree_test.go

@@ -0,0 +1,250 @@
+package trees
+
+import (
+	"fmt"
+	base "github.com/sjwhitworth/golearn/base"
+	eval "github.com/sjwhitworth/golearn/evaluation"
+	filters "github.com/sjwhitworth/golearn/filters"
+	"math"
+	"testing"
+)
+
+func TestRandomTree(testEnv *testing.T) {
+	inst, err := base.ParseCSVToInstances("../examples/datasets/iris_headers.csv", true)
+	if err != nil {
+		panic(err)
+	}
+
+	filt := filters.NewChiMergeFilter(inst, 0.90)
+	filt.AddAllNumericAttributes()
+	filt.Build()
+	filt.Run(inst)
+	fmt.Println(inst)
+	r := new(RandomTreeRuleGenerator)
+	r.Attributes = 2
+	root := InferID3Tree(inst, r)
+	fmt.Println(root)
+}
+
+func TestRandomTreeClassification(testEnv *testing.T) {
+	inst, err := base.ParseCSVToInstances("../examples/datasets/iris_headers.csv", true)
+	if err != nil {
+		panic(err)
+	}
+	trainData, testData := base.InstancesTrainTestSplit(inst, 0.6)
+	filt := filters.NewChiMergeFilter(inst, 0.90)
+	filt.AddAllNumericAttributes()
+	filt.Build()
+	filt.Run(trainData)
+	filt.Run(testData)
+	fmt.Println(inst)
+	r := new(RandomTreeRuleGenerator)
+	r.Attributes = 2
+	root := InferID3Tree(trainData, r)
+	fmt.Println(root)
+	predictions := root.Predict(testData)
+	fmt.Println(predictions)
+	confusionMat := eval.GetConfusionMatrix(testData, predictions)
+	fmt.Println(confusionMat)
+	fmt.Println(eval.GetMacroPrecision(confusionMat))
+	fmt.Println(eval.GetMacroRecall(confusionMat))
+	fmt.Println(eval.GetSummary(confusionMat))
+}
+
+func TestRandomTreeClassification2(testEnv *testing.T) {
+	inst, err := base.ParseCSVToInstances("../examples/datasets/iris_headers.csv", true)
+	if err != nil {
+		panic(err)
+	}
+	trainData, testData := base.InstancesTrainTestSplit(inst, 0.4)
+	filt := filters.NewChiMergeFilter(inst, 0.90)
+	filt.AddAllNumericAttributes()
+	filt.Build()
+	fmt.Println(testData)
+	filt.Run(testData)
+	filt.Run(trainData)
+	root := NewRandomTree(2)
+	root.Fit(trainData)
+	fmt.Println(root)
+	predictions := root.Predict(testData)
+	fmt.Println(predictions)
+	confusionMat := eval.GetConfusionMatrix(testData, predictions)
+	fmt.Println(confusionMat)
+	fmt.Println(eval.GetMacroPrecision(confusionMat))
+	fmt.Println(eval.GetMacroRecall(confusionMat))
+	fmt.Println(eval.GetSummary(confusionMat))
+}
+
+func TestPruning(testEnv *testing.T) {
+	inst, err := base.ParseCSVToInstances("../examples/datasets/iris_headers.csv", true)
+	if err != nil {
+		panic(err)
+	}
+	trainData, testData := base.InstancesTrainTestSplit(inst, 0.6)
+	filt := filters.NewChiMergeFilter(inst, 0.90)
+	filt.AddAllNumericAttributes()
+	filt.Build()
+	fmt.Println(testData)
+	filt.Run(testData)
+	filt.Run(trainData)
+	root := NewRandomTree(2)
+	fittrainData, fittestData := base.InstancesTrainTestSplit(trainData, 0.6)
+	root.Fit(fittrainData)
+	root.Prune(fittestData)
+	fmt.Println(root)
+	predictions := root.Predict(testData)
+	fmt.Println(predictions)
+	confusionMat := eval.GetConfusionMatrix(testData, predictions)
+	fmt.Println(confusionMat)
+	fmt.Println(eval.GetMacroPrecision(confusionMat))
+	fmt.Println(eval.GetMacroRecall(confusionMat))
+	fmt.Println(eval.GetSummary(confusionMat))
+}
+
+func TestInformationGain(testEnv *testing.T) {
+	outlook := make(map[string]map[string]int)
+	outlook["sunny"] = make(map[string]int)
+	outlook["overcast"] = make(map[string]int)
+	outlook["rain"] = make(map[string]int)
+	outlook["sunny"]["play"] = 2
+	outlook["sunny"]["noplay"] = 3
+	outlook["overcast"]["play"] = 4
+	outlook["rain"]["play"] = 3
+	outlook["rain"]["noplay"] = 2
+
+	entropy := getSplitEntropy(outlook)
+	if math.Abs(entropy-0.694) > 0.001 {
+		testEnv.Error(entropy)
+	}
+}
+
+func TestID3Inference(testEnv *testing.T) {
+
+	// Import the "PlayTennis" dataset
+	inst, err := base.ParseCSVToInstances("../examples/datasets/tennis.csv", true)
+	if err != nil {
+		panic(err)
+	}
+
+	// Build the decision tree
+	rule := new(InformationGainRuleGenerator)
+	root := InferID3Tree(inst, rule)
+
+	// Verify the tree
+	// First attribute should be "outlook"
+	if root.SplitAttr.GetName() != "outlook" {
+		testEnv.Error(root)
+	}
+	sunnyChild := root.Children["sunny"]
+	overcastChild := root.Children["overcast"]
+	rainyChild := root.Children["rainy"]
+	if sunnyChild.SplitAttr.GetName() != "humidity" {
+		testEnv.Error(sunnyChild)
+	}
+	if rainyChild.SplitAttr.GetName() != "windy" {
+		testEnv.Error(rainyChild)
+	}
+	if overcastChild.SplitAttr != nil {
+		testEnv.Error(overcastChild)
+	}
+
+	sunnyLeafHigh := sunnyChild.Children["high"]
+	sunnyLeafNormal := sunnyChild.Children["normal"]
+	if sunnyLeafHigh.Class != "no" {
+		testEnv.Error(sunnyLeafHigh)
+	}
+	if sunnyLeafNormal.Class != "yes" {
+		testEnv.Error(sunnyLeafNormal)
+	}
+
+	windyLeafFalse := rainyChild.Children["false"]
+	windyLeafTrue := rainyChild.Children["true"]
+	if windyLeafFalse.Class != "yes" {
+		testEnv.Error(windyLeafFalse)
+	}
+	if windyLeafTrue.Class != "no" {
+		testEnv.Error(windyLeafTrue)
+	}
+
+	if overcastChild.Class != "yes" {
+		testEnv.Error(overcastChild)
+	}
+}
+
+func TestID3Classification(testEnv *testing.T) {
+	inst, err := base.ParseCSVToInstances("../examples/datasets/iris_headers.csv", true)
+	if err != nil {
+		panic(err)
+	}
+	filt := filters.NewBinningFilter(inst, 10)
+	filt.AddAllNumericAttributes()
+	filt.Build()
+	filt.Run(inst)
+	fmt.Println(inst)
+	trainData, testData := base.InstancesTrainTestSplit(inst, 0.70)
+	// Build the decision tree
+	rule := new(InformationGainRuleGenerator)
+	root := InferID3Tree(trainData, rule)
+	fmt.Println(root)
+	predictions := root.Predict(testData)
+	fmt.Println(predictions)
+	confusionMat := eval.GetConfusionMatrix(testData, predictions)
+	fmt.Println(confusionMat)
+	fmt.Println(eval.GetMacroPrecision(confusionMat))
+	fmt.Println(eval.GetMacroRecall(confusionMat))
+	fmt.Println(eval.GetSummary(confusionMat))
+}
+
+func TestID3(testEnv *testing.T) {
+
+	// Import the "PlayTennis" dataset
+	inst, err := base.ParseCSVToInstances("../examples/datasets/tennis.csv", true)
+	if err != nil {
+		panic(err)
+	}
+
+	// Build the decision tree
+	tree := NewID3DecisionTree(0.0)
+	tree.Fit(inst)
+	root := tree.Root
+
+	// Verify the tree
+	// First attribute should be "outlook"
+	if root.SplitAttr.GetName() != "outlook" {
+		testEnv.Error(root)
+	}
+	sunnyChild := root.Children["sunny"]
+	overcastChild := root.Children["overcast"]
+	rainyChild := root.Children["rainy"]
+	if sunnyChild.SplitAttr.GetName() != "humidity" {
+		testEnv.Error(sunnyChild)
+	}
+	if rainyChild.SplitAttr.GetName() != "windy" {
+		testEnv.Error(rainyChild)
+	}
+	if overcastChild.SplitAttr != nil {
+		testEnv.Error(overcastChild)
+	}
+
+	sunnyLeafHigh := sunnyChild.Children["high"]
+	sunnyLeafNormal := sunnyChild.Children["normal"]
+	if sunnyLeafHigh.Class != "no" {
+		testEnv.Error(sunnyLeafHigh)
+	}
+	if sunnyLeafNormal.Class != "yes" {
+		testEnv.Error(sunnyLeafNormal)
+	}
+
+	windyLeafFalse := rainyChild.Children["false"]
+	windyLeafTrue := rainyChild.Children["true"]
+	if windyLeafFalse.Class != "yes" {
+		testEnv.Error(windyLeafFalse)
+	}
+	if windyLeafTrue.Class != "no" {
+		testEnv.Error(windyLeafTrue)
+	}
+
+	if overcastChild.Class != "yes" {
+		testEnv.Error(overcastChild)
+	}
+}

trees/trees.go

@@ -1,2 +1,26 @@
-// Package trees provides a number of tree based ensemble learners.
-package trees
+/*
+
+	This package implements decision trees.
+
+	ID3DecisionTree:
+		Builds a decision tree using the ID3 algorithm
+			by picking the Attribute which maximises
+			Information Gain at each node.
+
+		Attributes must be CategoricalAttributes at
+			present, so discretise beforehand (see
+			filters)
+
+	RandomTree:
+		Builds a decision tree using the ID3 algorithm
+			by picking the Attribute amongst those
+			randomly selected that maximises Information
+			Gain
+
+		Attributes must be CategoricalAttributes at
+			present, so discretise beforehand (see
+			filters)
+
+*/
+
+package trees