Golang ClasetInterface.GetClassIndex方法代码示例

// SelectRandomFeature if NRandomFeature is greater than zero, select and
// compute gain in n random features instead of in all features
func (runtime *Runtime) SelectRandomFeature(D tabula.ClasetInterface) {
	if runtime.NRandomFeature <= 0 {
		// all features selected
		return
	}

	ncols := D.GetNColumn()

	// count all features minus class
	nfeature := ncols - 1
	if runtime.NRandomFeature >= nfeature {
		// Do nothing if number of random feature equal or greater than
		// number of feature in dataset.
		return
	}

	// exclude class index and parent node index
	excludeIdx := []int{D.GetClassIndex()}
	cols := D.GetColumns()
	for x, col := range *cols {
		if (col.Flag & ColFlagParent) == ColFlagParent {
			excludeIdx = append(excludeIdx, x)
		} else {
			(*cols)[x].Flag |= ColFlagSkip
		}
	}

	// Select random features excluding feature in `excludeIdx`.
	var pickedIdx []int
	for x := 0; x < runtime.NRandomFeature; x++ {
		idx := numerus.IntPickRandPositive(ncols, false, pickedIdx,
			excludeIdx)
		pickedIdx = append(pickedIdx, idx)

		// Remove skip flag on selected column
		col := D.GetColumn(idx)
		col.Flag = col.Flag &^ ColFlagSkip
	}

	if DEBUG >= 1 {
		fmt.Println("[cart] selected random features:", pickedIdx)
		fmt.Println("[cart] selected columns        :", D.GetColumns())
	}
}

/*
computeGain calculate the gini index for each value in each attribute.
*/
func (runtime *Runtime) computeGain(D tabula.ClasetInterface) (
	gains []gini.Gini,
) {
	switch runtime.SplitMethod {
	case SplitMethodGini:
		// create gains value for all attribute minus target class.
		gains = make([]gini.Gini, D.GetNColumn())
	}

	runtime.SelectRandomFeature(D)

	classVS := D.GetClassValueSpace()
	classIdx := D.GetClassIndex()
	classType := D.GetClassType()

	for x, col := range *D.GetColumns() {
		// skip class attribute.
		if x == classIdx {
			continue
		}

		// skip column flagged with parent
		if (col.Flag & ColFlagParent) == ColFlagParent {
			gains[x].Skip = true
			continue
		}

		// ignore column flagged with skip
		if (col.Flag & ColFlagSkip) == ColFlagSkip {
			gains[x].Skip = true
			continue
		}

		// compute gain.
		if col.GetType() == tabula.TReal {
			attr := col.ToFloatSlice()

			if classType == tabula.TString {
				target := D.GetClassAsStrings()
				gains[x].ComputeContinu(&attr, &target,
					&classVS)
			} else {
				targetReal := D.GetClassAsReals()
				classVSReal := tekstus.StringsToFloat64(
					classVS)

				gains[x].ComputeContinuFloat(&attr,
					&targetReal, &classVSReal)
			}
		} else {
			attr := col.ToStringSlice()
			attrV := col.ValueSpace

			if DEBUG >= 2 {
				fmt.Println("[cart] attr :", attr)
				fmt.Println("[cart] attrV:", attrV)
			}

			target := D.GetClassAsStrings()
			gains[x].ComputeDiscrete(&attr, &attrV, &target,
				&classVS)
		}

		if DEBUG >= 2 {
			fmt.Println("[cart] gain :", gains[x])
		}
	}
	return
}