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pre-allocation

How can I preallocate a non-numeric vector in MATLAB?

I've often found myself doing something like this: unprocessedData = fetchData(); % returns a vector of structs or objects processedData = []; % will be full of structs or objects for dataIdx = 1 : length(unprocessedData) processedDatum = process(unprocessedData(dataIdx)); processedData = [processedData; processedDatum]; end Which, whilst functional, isn't optimal - the processedData vector is growing inside the loop. Even mlint warns me that I should consider preallocating for speed. Were data a vector of int8, I could do this: % preallocate processed data array to prevent growth in loop

2021-04-20 00:04:24    分类:问答    matlab   matlab-struct   pre-allocation

Preallocating arrays in Matlab?

I am using a simple for loop to crop a large amount of images and then storing them in a cell array. I keep getting the message: The variable croppedSag appears to change size on every loop iteration. Consider preallocating for speed. I have seen this several times before while coding in MATLAB. I have always ignored it and am curious how much preallocating will increase the runtime if I have, say, 10,000 images or a larger number? Also, I have read about preallocating in the documentation and it says to use zeros() for that purpose. How would I use that for the code below? croppedSag = {}

2021-04-05 06:55:15    分类:问答    arrays   matlab   memory-management   pre-allocation