[Numpy-discussion] finding eigenvectors etc

Javier Maria Torres javier.maria.torres@ericsson....
Wed Feb 20 08:56:20 CST 2008


Hi,

I would also like to know what Java package you're using. I find Weka PCA differs from Matlab (whereas previous experiments with Scipy PCA didn't show significant differences from Matlab), but I'm still looking into the cause.

Thanks, and greetings,

Javier Torres

-----Original Message-----
From: numpy-discussion-bounces@scipy.org [mailto:numpy-discussion-bounces@scipy.org] On Behalf Of devnew@gmail.com
Sent: miércoles, 20 de febrero de 2008 14:45
To: numpy-discussion@scipy.org
Subject: Re: [Numpy-discussion] finding eigenvectors etc


> How are you using the values? How significant are the differences?
>

i am using these eigenvectors to do PCA on a set of images(of faces).I sort the eigenvectors in descending order of their eigenvalues and this is multiplied with the  (orig data of some images viz a matrix)to obtain a facespace.
like
#pseudocode...
sortedeigenvectors=mysort(eigenvectors)
facespace=sortedeigenvectors*adjfaces  /* adjfaces is a matrix */

if i do this in python i get a facespace [[-1028755.44341439,  1480864.32750018,  1917712.0162213, -983526.60328021,
  -1662357.13091294,  -499792.41540038,   208696.97376238,
-916628.92613255,
  -1454071.95225114, -1563209.39113008,  -231969.96968212 , -768417.98606125]
 [ -866174.88336972,  1212934.33524067,   543013.86361006,
-1352625.86282073,
   -309872.30710619 ,  466301.12884198,
216088.93319292 ,-1512378.8688779,
   2581349.03171275,  1797812.01270033,  1876754.7339826 ,
751781.8166291 ]
 [  -57026.32567001 ,  -69918.94570563,  -399715.51441018, -233720.8360051,
    188227.41229887,   177341.47889165 ,  -65241.23138424 ,
-311917.28253664,
   1133399.70627111,  1089028.99019462,   684854.41725944 ,
413465.86494352]
 [  405955.15245412,   562832.78296479 ,  864334.63457882 ,
629752.80210603,
    894768.52572026,   578460.80766675 ,  629146.32442893 ,
768037.57754708,
   -485157.28573271, -1718776.11176486 , -780929.18155991 , -165391.19551137]]

whereas the same steps
in java
[
[-516653.73649950844, 274000.54127598763, -108557.2732037272, -799041.4108906921, -495577.7478765989, -49125.38109725664, -162041.57505147497, -917033.3002665655, 1207264.8912226136, 1384551.3481945703, 1056098.9289163304, 357801.9553511339], [-956064.0724430305, 1424775.0801567277, 898684.8188346579, -1385008.5401600213, -514677.038573372, 387195.56502804917, 281164.65362325957, -1512307.8891047493, 2114204.697920214, 1280391.7056360755, 1650660.0594245053, 554096.482085637], [-666313.7580419029, 1365981.2428742633, 2011095.455319733, -453217.29083790665, -1199981.2283586136, -358852.32104592584, 375855.4012532809, -311436.16701894277, -2033000.776565753, -2418152.391663846, -847661.841421182, -926486.0374297247], [593030.0669844414, 121955.63569302124, 124121.99904933537, 697146.7418886195, 1321002.514808584, 743093.1371151333, 493712.52017493406, 767889.8563902564, 487050.6874229272, -641935.1621667973, -310387.14691965195, 246026.0999929544] ]

such difference causes diff results in all calculations involving the facespace

dn
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