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Shuffling a list in a loop once, then running it multiple times

edited January 3 in OpenSesame


I have a loop that runs several times that should random a variable value (all values are letters, in my case). I have 18 values, and the loop runs 7 times in each sequence. Also, I don't want the same value to appear more than once. I thought I should use the "shuffle" command in the loop item and pick "sequential" under "Order", but while it does seem to shuffle the list, I guess the loop runs itself and reshuffles the list in each loop-run so I end up getting a certain letter (variable value) more than once in each sequence, occasionally.

Any idea what am I getting wrong?

Thank you,


  • Hi Omer,

    Hmm, it's not entirely clear to me what you want to do.

    • The title of your discussion suggests that you want to determine the order of a loop once, and then run the loop in that same order multiple times. Do I understand that correctly?
    • What kind of constraints do you want to apply to the order? Right now, target_letter has 18 unique values, so I don't see how repetitions within a loop can occur, nor how you can avoid repetitions if you run the loop 7 times.


    There's much bigger issues in the world, I know. But I first have to take care of the world I know.

  • Hey Sebastiaan,

    First, thank you for you answer. I havn't managed to get to this project lately but I'm getting back to it now (that's why it took me so long to respond back. apologies).

    So I guess I wasn't clear enough as of what is it that I'm trying to achieve. Maybe I'll open by briefly describing how 1 trial in my experiment should look like -
    1. A letter (from a bank of 18 unique letters in total) should appear.
    2. 4 consecutive (timed) tasks appear.
    3. This sequence of events should appear for 6 more times or 7 in total, so - 7 letters and 28 tasks in total.
    4. Subjects will report the list of letters into a text input form.

    That's the basic structure of a trial in my experiement.
    Now, for what I can't figure out - I want the order of letters to be random and with no repeats within each trial. From your 2nd note I understand that my understanding wasn't correct - the way it's built right now (same as in the picture above) I was basicly creating a different list each time and calling the 'target_letter' gave me the first value of the list each time, that's why I'm getting repetitions.

    While trying to fix this issue now, I tried to call 'target_letter' more than once within a loop to see if that would do the trick but that resulted in getting the same value for 'target_letter' for the whole loop. Plus, it felt like the design was quite 'stupid' so I'm not sure that's the way I should be heading with this.

    I hope this provides more info,
    Thanks again,

  • Hi Omer,

    If you put all letters in one row each (column name is target letter or whatever), and set repeat to something around 0.4. The loop will iterate 7 times (tweak the value to get exactly 7 and not 6 or 8) and you have 7 unique letters.

    Does that help?


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