Property/field arithmetics on object/struct array in Matlab

Question

Given two struct arrays A and B with field f1:

A = struct('f1',{1,2,3})
B = struct('f1', {4,5,6})

you can assign the contents of the f1 fields of struct array A to the fields of B by

[B.f1] = A.f1

but I cannot figure out what to do if you want to perform arithmetics on the field, for instance if you want to store the negative of the f1 fields of A in B.

[B.f1] = -A.f1

does not work, you need to first concatenate the elements of A in order for the operator to work

-[A.f1]

but then the result is a vector, which somehow you need to "unwrap" in order to match the number of output arguments.

Johan · Accepted Answer · 2012-03-30 14:58:55Z

3

You can use num2cell:

tmp=num2cell(-[A.f1]);
[B.f1]=tmp{:};

Result:

B.f1

ans =
    -1
ans =
    -2
ans =
    -3

edited Mar 30, 2012 at 14:58

Johan

3803 silver badges9 bronze badges

answered Mar 30, 2012 at 13:20

Oli

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1 Comment

Johan Over a year ago

Thanks, I tried using deal but without num2cell and it appears that it's actually num2cell that does all the heavy lifting. It's not even necessary to use deal, [B.f1]=tmp{:}; works just as well.

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