MATLAB Answers


Adding multiple fields and values to structure array

Asked by Lilly Aurelius on 19 Apr 2019
Latest activity Commented on by Lilly Aurelius on 20 Apr 2019
I have a code in which I am looping through many files, and for each file, I'm adding fields and values to a structure array.
The code is quite repetitive and I'm wondering if there is a way to shorten it a bit.
Right now it looks like this:
data(k).pairNum = pairNum;
data(k).level = level;
data(k).trialNum = trialNum;
data(k).success = win;
data(k).numWins = numWins;
data(k).totalTime = totalTime;
data(k).timeUntilSuccess = timeUntilSuccess;
data(k).totalTime = totalTime;
data(k).initialSpread = initialSpread;
data(k).initialCOM = initialCOM;
data(k).D1_distance = D1_distance;
data(k).D2_distance = D2_distance;
But im just curious if there is a way to make it work by doing something like this:
data(k).[pairNum, level, trialNum, win, numWins, totalTime] = pairNum, level, trialNum, win, numWins, totalTime;


One easy way to avoid this would be to define those variables as fields of a scalar structure S, rather than as separate variables. Then merging them with the non-scalar output structure is just one simple assignment data(k) = S;
I dont 100% understand what you mean, could you elaborate? Sorry, I'm a bit of a novice...

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1 Answer

Answer by Walter Roberson
on 19 Apr 2019
 Accepted Answer

Provided you are setting all of the fields of data(k), then you can use
data(k) = struct('PairNum', pairNum, 'level', level, 'trialNum', trialNum, ....)
which is no shorter.
Or you could use
names = {'pairNum', 'level', 'trialNum', 'success' ... };
and then in the loop
data(k) = cell2struct( {pairNum, level, trialNum, win, ...}, names, 2);
Again, these only work if you are setting all of the fields.
If you have all of the values ahead of time you can create the entire struct:
data = struct('PairNum', cell_with_all_pairnum, 'level', cell_with_all_level, ....)
The number of structure members created will be the same as the number of entries in the cells you pass.
If any of the fields are the same for all of the members, then instead of a cell, you can pass the actual value at that location, not in a cell.

  1 Comment

Thank you! Great answer.
I have over 50 fields so I may just stick with individual lines for each field, to avoid oner super long line of code.

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