Historically there have been all kinds of "numerical analysis" difficulties in programming matrix algebra applications like factor analyses.
Since you are on an SPSS list, are you just using Visual Basic to call SPSS routines, or are you doing the matrix algebra in Visual Basic?
_IFF_ I recall correctly the factor loading matrix that one can read in or output is the unrotated factor matrix. so you do not have to you only have to create the R matrix once and do the extraction once.
aside: I have never used /matrix with a 'fac" argument. n the rare occasions that I also wanted an oblique rotation, I just cannibalized the syntax for the ordinary varimax rotation and tweaked it by changing the one argument.
If you are using SPSS to do the actual calculations try something like this untested approach to see if I am correct. draft 5 blocks of syntax. run 4 factor analyses the first 3 just differ in what is on the /rotation specification and what file the loadings are written to 1) /rotation = norotate /matrix= out (fac= ... 2) /rotation = varimax /matrix= out (fac=... 3) /rotation = promax /matrix= out (fac=...
for these 2 blocks the file of factor loadings is that was written in block 1 4) /matrix= in (fac=...)/rotation = varimax 5) /matrix= in (fac=...)/rotation = promax
Check and see which loadings files are identical.
Also I would suggest that you Google "nabble SPSSX" and join the discussion list. It is much more active than this newsgroup.
Then post about what the goal of your effort actually is. Maybe VB is optimal,maybe a macro, maybe python, maybe OMS.
Art Kendall Social Research Consultants
On 4/21/2013 1:54 PM, avi wrote: > Le dimanche 21 avril 2013 13:56:19 UTC+3, avi a écrit : >> Hello, >> >> >> >> Is there a relatively simple way for converting a Varimax matrix of loadings to an oblique one? >> >> >> >> Thanks >> >> >> >> Avi > > I'm writing in Visual basic an application for factor analysis. I've already done the Varimax rotation and I look for some way to perform an oblique one without beginning fro scratch > > Avi >