How to add array as a single element to another array in MATLAB?

Question

I have a function that returns arrays of struct arrays. I want to call this function repeatedly, appending the returned value to another array, but I'd like to append the returned value as a single element of the larger array. cat() doesn't seem to work for me because it appends every element of the returned value individually to the larger array.

In the context of the following example, how do I add foo to bar as a single element of bar?

foo(1).id = 1;
foo(1).v = 'a';
foo(2).id = 2;
foo(2).v = 'b';

bar = [];
bar = cat(1, bar, foo); % Adds each element of foo individually

rayryeng · Accepted Answer · 2016-07-20 21:00:15Z

3

If I am interpreting your question correctly, you would like each element in this "array" to be this array of structures that's returned by the function. What you are doing in your code below is simply creating a larger structure array and appending each of the elements in the structure array to this larger structure array.

You probably want to use cell arrays instead. Simply put, change bar = []; to bar = {};. When you're done, you can access each element by using curly braces (i.e. {}) and the index of where you want to access:

% Your example data
foo(1).id = 1;
foo(1).v = 'a';
foo(2).id = 2;
foo(2).v = 'b';

% Add another one for proof of concept
foo2(1).id = 3;
foo2(1).v = 'c';
foo2(2).id = 4;
foo2(2).v = 'd';

bar = {}; % Change
bar = cat(1, bar, foo);
bar = cat(1, bar, foo2); % Add another nested structure array in

baz = bar{1}; % Get the first nested structure array
baz2 = bar{2}; % Get the second nested structure array

edited Jul 20, 2016 at 21:00

answered Jul 20, 2016 at 19:24

rayryeng

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3 Comments

pretzlstyle Over a year ago

Yes, for anyone coming from anther language where arrays are indexed by objects (arrays within arrays are interpreted as single objects rather than a matrix "row", or whatever), the cell array is your savior.

rayryeng Over a year ago

@jphollowed Thanks :) An upvote wouldn't come amiss :D... optional of course.

rayryeng Over a year ago

@jphollowed lol that was quick. Thank you. BTW if it sounded like I was begging, please ignore. You have the right to do whatever you want.

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