PSPP-BUG: Errata corrige: SVD matrix function

[Frans Houweling]

Hi,

 as I (perhaps) understand now, SVD yields more than one possible solution.

Excuse me. The bug is on me.

Best regards

frans

On 6/19/22 19:18, Frans Houweling wrote:

Hi,

 not sure this is a bug.

 I was studying the matrix facility and trying to simulate a correspondence analysis. The coordinates on the second dimension had the wrong sign. I narrowed it down to a difference in the output of SVD.

Actual output:


SET PRINTBACK = ON.

SHOW SYSTEM.

System Information

Version	GNU pspp 1.6.0
Host System	x86_64-pc-linux-gnu
Build System	x86_64-pc-linux-gnu
Locale Directory	/usr/local/share/locale
Compiler Version	11.3.0

MATRIX.
COMPUTE Z = {.0864567551, .0285087603, -.0869963370;
 .0383529410, .1082579438, -.1353350560;
 .0441034059, -.0658036806, .0369188203;
 -.0850336980, -.0154156630, .0727911485;
 -.0454583792, -.0647514858, .0960927767}.

PRINT Z /FORMAT = F10.7.

Z
.0864568 .0285088 -.0869963
.0383529 .1082579 -.1353351
.0441034 -.0658037 .0369188
-.0850337 -.0154157 .0727911
-.0454584 -.0647515 .0960928

CALL SVD(Z, U, sigma, V).

PRINT sigma  /FORMAT = F10.7.

sigma
.2652708 .0000000 .0000000
.0000000 .1135421 .0000000
.0000000 .0000000 .0000000

PRINT U  /FORMAT = F10.7.

U
-.4386666 .4237559 .6866002
-.6516462 -.3550114 -.4516196
.1603076 .6724694 -.3645709
.3711005 -.4884741 .4002276
.4685240 .0597979 -.1775551

PRINT V  /FORMAT = F10.7.

V
-.4097795 .8058464 -.4274252
-.4887795 -.5896041 -.6430098
.7701788 .0545755 -.6354889

END MATRIX.

Expected output (R: svd(Z)   v. https://www.displayr.com/math-correspondence-analysis/ ):

$d
[1] 2.652708e-01 1.135421e-01 2.718254e-17

$u
                          [,1]        [,2]       [,3]
Some primary        -0.4386666 -0.42375592 -0.3714480
Primary completed   -0.6516462  0.35501142 -0.4906752
Some secondary       0.1603076 -0.67246939 -0.2423522
Secondary completed  0.3711005  0.48847409 -0.3785281
Some tertiary        0.4685240 -0.05979793 -0.6474922

$v
                      [,1]        [,2]       [,3]
Glance          -0.4097795 -0.80584644 -0.4274252
Fairly thorough -0.4887795  0.58960413 -0.6430097
Very thorough    0.7701788 -0.05457549 -0.6354889