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how to preallocate large logical array

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Michael
Michael 2012-3-13
评论： Image Analyst 2018-6-23
Hi
I'm trying to pre-allocate a huge logical matrix but I can't work out how to do it without creating a normal matrix then converting it (this intermediate step uses too much memory).
I've been trying A = zeros(50,50,50,50,50, 'uint8'); Which works to create one from 0-255 but I can't find what to write in the quotes to make it logical rather than numeric, and suspect there may be some kind of trick that I'm missing.
Thanks Mike

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Image Analyst
Image Analyst 2012-3-13
A = false(numRows, numCols); % Or can use true()

更多回答（2 个）

James Tursa
James Tursa 2012-3-13
Another alternative (assumes that all of the elements are filled in downstream):
A = uninit(numRows, numCols, 'logical');
You can find uninit on the FEX here:
http://www.mathworks.com/matlabcentral/fileexchange/31362-uninit-create-an-uninitialized-variable-like-zeros-but-faster
Ingrid
Ingrid 2018-6-23
I am not sure in which release it started working but at least in R2018a
A = zeros(50,50,50,50,50, 'logical');
works.
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Image Analyst
Image Analyst 2018-6-23
Or use false() as I suggested:
A = false(50, 50, 50, 50, 50);
It's a bit simpler and more direct.

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