Randomization with constraints

[trab24]

Hi, I found a work around for this.
Say I have a group of 4 pictures that must be displayed 3 times in random order with no overlap (4 pics, 4 pics, 4 pics). Instead of using list of stimuli I use WGR to randomize by assigning each repetition of the 4 items a WGR. Then select one of the pics and assign it a WGR or 0 in all repetitions. by strategically positioning that pic overlap can be avoided. So it would look like this (working with pic 3):
WGR STIMULI
1 pic 1
1 pic 2
1 pic 4
0 pic 3
______________________
2 pic 1
2 pic 2
0 pic 3
2 pic 4
_______________________
0 pic 3
3 pic 1
3 pic 2
3 pic 4

It's not pure randomization but it works for me.

[Dianna]

I am having a similar issue with an experiment I want to run with directRT 2010.

I am trying to randomize a task in which there are 24 trials with sets of images within each trial. There are images of 4 people, each with 6 different types of images (which make 24 trials in total). I want to make it so that all 4 of the same type of image do not occur all within the first half or all within the second half of the task. I do not want to constrain it so much by making 2 blocks and putting 2 of the people within the same block, and then just randomizing the order of the blocks (because there may be some effect of always putting the same 2 people together). Do you have any suggestions as to how I could do this?