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Author Topic: Bug in PCA operator output  (Read 1393 times)
Victor
Guest
« on: July 27, 2008, 06:19:54 AM »

Input file:

X1 X2 X3
1. 1. 0.
1. 1. 1.
1. 1. 2.
0. 0. 0.
0. 0. 1.

Experiment:

<operator name="Root" class="Process" expanded="yes">
    <operator name="ExampleSource" class="ExampleSource">
        <parameter key="attributes"   value="C:\Documents and Settings\Victor\My Documents\test_pca\input.aml"/>
    </operator>
    <operator name="PCA" class="PCA">
    </operator>
    <operator name="ModelApplier" class="ModelApplier">
        <list key="application_parameters">
        </list>
        <parameter key="keep_model"   value="true"/>
    </operator>
    <operator name="CSVExampleSetWriter" class="CSVExampleSetWriter">
        <parameter key="column_separator"   value=","/>
        <parameter key="csv_file"   value="C:\Documents and Settings\Victor\My Documents\test_pca\output.csv"/>
    </operator>
</operator>

The log shows:

Principal Components:
Variance Threshold: 0.95
PC 1:  + 0.439 * X1 - 0.554 * X2 + 0.707 * X3
PC 2:  + 0.439 * X1 - 0.554 * X2 - 0.707 * X3
PC 3:  + 0.784 * X1 + 0.621 * X2 - 0.000 * X3
(created by PCA)

I think the correct components are transpose of this, so the log should show:

PC1 = 0.439*X1 + 0.439*X2 + 0.784*X3
Pc2 = -0.554*X1 - 0.554*X2 ...




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Victor
Guest
« Reply #1 on: July 28, 2008, 03:32:13 PM »

Just to clarify - the incorrect (transposed) values are printed only in the log.

The PCA matrix on the screen (tab Eigenvectors view) is displayed correctly.
The next step, model applier, also uses the correct values.

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Ingo Mierswa
Administrator
Hero Member
*****
Posts: 1226



WWW
« Reply #2 on: July 29, 2008, 04:25:28 PM »

Hi Vector,

thanks for sending this in. And especially for the additional note - I got a slight shock before you mentioned that it is only transposed in the log out. Puh... Cheesy

I have changed the logging output and the fixed version is available via CVS in a few hours.

Cheers,
Ingo









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