MATLAB Answers

Changing data from long form to short form

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Rachel Nesbit
Rachel Nesbit on 11 Sep 2019
Edited: Steven Lord on 12 Sep 2019
Hi all,
I wondered if someone might be able to help - with what might seem like a super easy tast.
I have data in longform i.e. (a simple example of what I have below, example 1), but I ideally need it in short form i.e. one row per participant see example 2.
Example 1.
Participant_ID Trial RT
1 1 342
1 2 346
1 3 534
2 1 242
2 2 131
2 3 531
Example 2.
Participant_ID 1_RT 2_RT 3_RT
1 342 346 534
2 242 131 531
Is there a simple way I can do this?
Thank you in advance,
Rachel

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Answers (3)

Steven Lord
Steven Lord on 12 Sep 2019
Edited: Steven Lord on 12 Sep 2019
Participant_ID = [1; 1; 1; 2; 2; 2];
Trial = [1; 2; 3; 1; 2; 3];
RT = [342; 346; 534; 242; 131; 531];
t = table(Participant_ID, Trial, RT);
unstackedTable = unstack(t,'RT','Trial');

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Rik
Rik on 11 Sep 2019
You can use the participant ID and trial ID as the indices and either use accumarray or sub2ind to fill the matrix with the values. I would suggest sub2ind if you can guarantee that every combination of trial and participant is unique.

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Walter Roberson
Walter Roberson on 11 Sep 2019
Under the assumption that all of the information for each participant is gathered together and that there are exactly the same number of data points per participant, then:
[Particpant_ID(1:number_of_trials:end), reshape(RT, number_of_trials).']

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