What's wrong with my preallocation of images?

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Iana Ladygina
Iana Ladygina 2019-12-20
评论： Walter Roberson 2019-12-30
folders = dir("photos");
folders = string({folders.name});
folders = folders(~startsWith(folders,"."))
% Preallocate the structure crashImages
crashImages(length(folders)) = struct("Name",folders(end),"Images",cell(1));
for k = 1:length(folders)
photos = dir("photos\" + folders(k));
photos = string({photos.name});
photos = photos(~startsWith(photos,'.'));
% preallocate the cell array images
images = cell(length(photos),1);
for kk = 1:length(photos)
im = imread("photos\" + folders(k) + "\" + photos(kk));
images{kk} = im;
end
crashImages(k).Name = folders(k);
crashImages(k).Images = images;
clear images
end
crashImages
I get the error that the cell arrays in the Image field do not have the correct sizes. What could be the problem?
  2 个评论
Catalytic
Catalytic 2019-12-20
It is generally more informative to copy/paste your error messages (all of them) than to summarize them in your own words. That way, we can see for example what line of code was to blame.
Stephen23
Stephen23 2019-12-30
编辑：Stephen23 2019-12-30
Simpler and more robust than using startsWith:
S = dir("photos");
folders = setdiff({S.name},{'.','..'});
Note that you can easily use the same structure that dir returns:
S = dir('photos');
S(ismember({S.name},{'.','..'})) = [];
for k = 1:numel(S)
...
S(k).image = images;
end
Also you should use fullfile rather than concatenating strings together.
"I get the error that the cell arrays in the Image field do not have the correct sizes. What could be the problem?"
If you don't show us the complete error message then we have to guess what the problem is.

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回答（1 个）

Matt J
Matt J 2019-12-20
编辑：Matt J 2019-12-20
Maybe you meant to have,
crashImages(length(folders)) = struct("Name",folders{end},"Images",cell{1});
  4 个评论
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Iana Ladygina
Iana Ladygina 2019-12-30
Sorry, may be I don't understand it well, but how is fullfile() function related to the preallocation?
Walter Roberson
Walter Roberson 2019-12-30
Your file reference is coming out wrong, so dir is returning empty, so length is 0, so images would be an empty cell. You then interpreted that as being the incorrect size.

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