exceedance probability: WARNING!

[lionel-rigoux]

From @GoogleCodeExporter on October 7, 2015 9:29

This thread is a warning on the use of exceedance probabilities (EPs).

By default, a RFX-BMS will try to compute exceedance probabilities using 
compiled C code for sampling on a Dirichlet distribution (spm_gamrnd.c). If the 
compilation has not been done, this attempt will fail and the toolbox will 
resort to a normal approximation of EPs.

The quality of this approximation increases with the ratio of number of 
subjects divided by the number of models. When this ratio gets smaller than 
one, the approximation can become slightly overconfident.

Note that the toolbox prompts the user with the following message: 'Warning: 
exceedance probabilities are approximated!'.


In such cases, users would be well advised to re-compile the code, so that 
EPs are correctly estimated. In some instances, it suffices to replace the 
files 'spm_gamrnd*.*' in the directory '/stats&plots/spm_code' with the 
attached files. If this does not work (if the warning message still appears), 
please follow this thread and we will find a solution.

Original issue reported on code.google.com by [email protected] on 28 Jan 2014 at 1:53

Attachments:

• spm_gamrnd.c
• spm_gamrnd.mexmaci64
• spm_gamrnd.mexw64
• spm_gamrnd.mexa64
• spm_gamrnd.mexglx
• spm_gamrnd.mexmaci
• spm_gamrnd.mexw32

Copied from original issue: lionel-rigoux/mbb-vb-toolbox#5

[lionel-rigoux]

From @GoogleCodeExporter on October 7, 2015 9:29

Note: this may affect the beta testers of the multi-source version of the 
toolbox!

Original comment by [email protected] on 28 Jan 2014 at 1:55

[lionel-rigoux]

From @GoogleCodeExporter on October 7, 2015 9:29

Exceedance probability: resolved.

The default sampling approach for EPs has now been changed to incorporate novel 
matlab's pre-compiled smapling routines. RFX-BMS only reverts to SPM sampling 
routines if VBA cannot find matlab's sampling routines.

NB: the new implementation using matlab's sampling routines is about 100 times 
faster (because it avoids loops)!

Original comment by [email protected] on 29 Jul 2014 at 9:39