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static private ZScored ( IArrayView |
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| examples | IArrayView |
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| means | IArrayView |
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| standardDeviations | IArrayView |
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| return | IArrayView |
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internal static IArrayView<Example> ZScored(IArrayView<Example> examples,
out IArrayView<double> means,
out IArrayView<double> standardDeviations)
{
// compute means and standard deviations
int numFeatures = examples[0].Features.Count;
IArray<double> meansArray = Arrays.New<double>(numFeatures), standardDeviationsArray = Arrays.New<double>(numFeatures);
double mean;
for (int i = 0; i < numFeatures; i++)
{
standardDeviationsArray[i] = examples.Select(e => e.Features[i]).StandardDeviation(out mean);
meansArray[i] = mean;
}
means = meansArray;
standardDeviations = standardDeviationsArray;
// z-score the examples
return examples.Select(e => e.ZScored(meansArray, standardDeviationsArray)).ToIArray();
}
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Example::ZScored ( IArrayView |
public static void Run()
{
var ex = new Example(2, new double[] { 1, 3, 2 });
// WithClass test
if (ex.WithClass(5).Class != 5 || !ex.WithClass(5).Features.SequenceEqual(new double[] { 1, 3, 2 }))
throw new Exception("WithClass failed");
// ZScore test
var examples = new Example[] {
new Example(1, new double[] { 1, 7 }),
new Example(3, new double[] { 5, 5 }),
new Example(1, new double[] { 3, 3 }),
}.AsIArray();
IArrayView<double> means, sds;
var zscored = examples.ZScored(out means, out sds);
if (!means.SequenceEqual(new double[] { 3, 5 }))
throw new Exception("Bad means");
if (!sds.SequenceEqual(new double[] { 2, 2 }))
throw new Exception("Bad standard deviations");
foreach (int i in examples.Indices())
foreach (int j in examples[0].Features.Indices())
if (zscored[i].Features[j] != (examples[i].Features[j] - means[j]) / sds[j])
throw new Exception("Bad zscore value");
}