strings pseudo-randomization plus constraints

Dear all,

I'm about to randomize my stimuli for an experiment. Each stimulus corresponds to an audio-file, whose name might be like the following:

ALPHA_BETA_AA_01 or 
ALPHA_BETA_BB_01 or 
ALPHA_BETA_CC_01 or ... 
ALPHA_BETA_CC_48

I have six conditions with 48 stimuli each, plus six conditions with 12 stimuli each.

My goal is to randomize my conditions.

I use to import my list of 360 strings with textread, so that I have

M <360x1 cell>

I'm looking for a way to randomize my stimuli so that no more that three stimuli of the same condition would appear in succession.

As a clarification, the labelling I'm using for my files (i.e. ALPHA_BETA_AA_1) stands for:

ALPHA_BETA  %is the name of the file
_AA         %is the name of the condition
_01         %is the ordering number

Any suggestion is highly appreciated!

Sincerely,

Udiubu

P.S. I found the "shake" function by Jos van der Geest on the File Exchange, but still, I don't know how to constrain my script.

[Walter Roberson]

Are the six conditions with the 48 stimuli named differently than the 6 with the 12 stimuli? If not then do the ones that are named the same between the two groups to be considered the same or different?

[Ubu]

Hi Walter,

Thanks for your answer.

Actually, the email before was silghtly misleading.

I can easily rename my files, so that they can look this way:

Condition AA would be:

AA_01_ALPHA_BETA

AA_02_DELTA_GAMMA

AA_48_PSI_OMEGA

Condition BB would be

BB_01_AAAA_BBBB

BB_02_DDD_GGGG

BB_48_PPP_OMEGA

Condition ZZ (with 12 stimuli) would be:

ZZ_01_XXX_SSS

ZZ_02_LLL_GGGG

ZZ_12_AAQ_QQQQ

For all conditions - those with 12 stimuli included - the first two letters idicate the conditions, the number is the ordering, the two strings are different for each stimulus for each condition.

I hope this help, Walter!

Answer 1

[Walter Roberson]

codes = [101:148,201:212]; 

need_valid = true;
while need_valid
  randcodes = codes(randperm(length(codes)));
  need_valid = ~isempty(strfind(floor(randcodes ./ 100), [0 0]));
end

At this point, randcodes encodes the ordering, with the hundreds digit of each location indicating which of the two conditions it is, and with the last two digits indicating the stimuli within the condition.