I want to do
myCellArray = myCcellArray{indices}
where indices is just 0s and 1s, with same number of elements as the number of rows in myCellArray, but it doesn't work. What should I do?
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3 Answers
You need to use parenthesis instead of curly braces to do the indexing.
>> arr = cell(2,2);
>> arr{1,1} = magic(4);
>> arr{1,2} = 'Hello';
>> arr{2,1} = 42;
>> arr{2,2} = pi;
>> arr
arr =
[4x4 double] 'Hello'
[ 42] [3.1416]
>> idx = logical(zeros(2,2));
>> idx(1,1) = true;
>> idx(2,2) = true;
>> arr(idx)
ans =
[4x4 double]
[ 3.1416]
Comments
If you want to slice a cell-array, use parentheses. Example:
%# random cellarray of strings, and a logical indices vector
myCcellArray = cellstr(num2str((1:10)','value %02d')); %'
indices = rand(size(myCcellArray)) > 0.5;
%# slicing
myCellArray = myCcellArray(indices)
Comments
What amro said is right, you should use parentheses.
But another critical thing is to use booleans not numeric 1 and 0 here.
so if you have numbers
I = [0 0 0 1 0 1]
you should use
myCellArray(I~=0)
to index it. Confusingly, a boolean array is displayed as ones and zeros in Matlab, although it is represented quite differently internally.
1 Comment
Andrew Janke
Technically, a logical array is represented internally the same as a uint8 array of ones and zeros (one byte per element, set to 0x00 or 0x01). It just has a different datatype flag, so it's interpreted differently. You can verify this by using
mxGetElementSize and mxGetData to examine the two array types in a MEX function.