Sorting Struct elements in Numerical order

2019 6 6
2 个回答
回答已采纳
更新时间：2021 5 4
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I have a program which takes some pictures in a struct and performs some pixel counting in each of the pictures. After running the program when I see the struct, the elements are not arranged in the way I want them to be. Here is the code-
img_folder = ('C:\Users\mm\work\blackpixelcount');
filenames = dir(fullfile(img_folder,'*.JPG'));
Total_image = numel(filenames);
for i= 1:Total_image
f = fullfile(img_folder,filenames(i).name);
im= imread(f);
bw= imbinarize(im);
out=nnz(~bw);
get(i)=out;
end
after running the code I see the struct and its sorted as given below-
x.JPG
Now I want the elements to be sorted in numerical ascending order (1,2,3.....9,10,11,12..).
I might be makigs some mistakes there, since I am biggener in matlab. Help will be really appreciated.

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KSSV
KSSV 2019-6-6

2 个投票

9 个评论
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Md Farhad Mokter
Md Farhad Mokter 2019-6-6
Tried with the command 'natsortfiles({filenames.name});'
did not work.
Stephen23
Stephen23 2019-6-6
@Md Farhad Mokter: did you first download the function from the link that KSSV gave you, and then unzip the zip file onto your MATLAB path (e.g. into the current directory) ?
Jan
Jan 2019-6-6
@Md Farhad Mokter: "Did not work" is too lean to be clear. Please explain what you observe.
Stephen23
Stephen23 2019-6-6
Md Farhad Mokter's "Answer" moved here:
I used the given command at the end of program,
b= natsortfiles({filenames(:).name};
I got the names in b variable sorted in natural order. Now I want to sort the elements in "filenames" before the 'for loop' starts. I tried this-
img_folder = ('C:\Users\mm\work\blackpixelcount');
filenames = dir(fullfile(img_folder,'*.JPG'));
b= natsortfiles(filenames);
Total_image = numel(b);
for i= 1:Total_image
f = fullfile(img_folder,b(i).name);
im= imread(f);
bw= imbinarize(im);
out=nnz(~bw);
get(i)=out;
end
and I got error : "Error using natsortfiles (line 123)
First input <X> must be a cell array."
Stephen23
Stephen23 2019-6-6
编辑：Stephen23 2019-6-6
"I used the given command at the end of program, "
b= natsortfiles({filenames(:).name};
But this is what you actually have in your code:
b= natsortfiles(filenames);
Note that the output of natsortfiles is a cell array of character vectors, so your line
fullfile(img_folder,b(i).name);
will also throw an error (because you try to access a cell array as if it was a structure).
Also note that the natsortfiles documentation includes examples of how to use it. I recommend that you read its documentation, so you can avoid these basic errors.
Md Farhad Mokter
Md Farhad Mokter 2019-6-6
@Stephen Codeldick Sir, I used that command at the end of program, it worked. But the 'filenames' variable remained same as before. So, I tried to put it before the loop and thats what I gave here.
Even. putting the command below command returns error: Dot indexing is not supported for variables of this type.
b= natsortfiles({filenames(:).name};
Stephen23
Stephen23 2019-6-6
编辑：Stephen23 2019-6-6
"But the 'filenames' variable remained same as before"
Sure. You only define it once (on the second line of your code), nowhere else in your code do you make any changes to filenames. You assigned the output of natsortfiles to variable b, so b contains the sorted filenames.
Follow the examples in the natsortfiles documentation.
Jan
Jan 2019-6-6
编辑：Jan 2019-6-6
@Md Farhad Mokter: Use this:
img_folder = ('C:\Users\mm\work\blackpixelcount');
filelist = dir(fullfile(img_folder,'*.JPG'));
filenames = {filelist.name}; % added
b = natsortfiles(filenames);
Total_image = numel(b);
getList = zeros(1, Total_image); % Pre-allocate, avoid "get" as name
for i = 1:Total_image
f = fullfile(img_folder, b{i}); % not b(i).name
im = imread(f);
bw = imbinarize(im);
getList(i) = nnz(~bw);
end
get is an important Matlab command, so avoid using it as name of a variable.

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Md Farhad Mokter
Md Farhad Mokter 2019-6-6

0 个投票

@Stephen Cobeldick sir,
it worked !!
After reading the documentation part once again, I edited the code in line 3 and line 4.
img_folder = ('C:\Users\mm\work\blackpixelcount');
filenames = dir(fullfile(img_folder,'*.JPG'));
[~,ndx] = natsortfiles({filenames.name});
filenames = filenames(ndx);
Total_image = numel(filenames);
for i= 1:Total_image
f = fullfile(img_folder,filenames(i).name);
im= imread(f);
bw= imbinarize(im);
out=nnz(~bw);
get(i)=out;
end
Now It is all good. My apologies for mistakes and thank you so much.
@Jan, Thank you for the help. I will now give it a try.

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