Problem Creating Structure Field with For Loop

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Allen Hammack
Allen Hammack 2022-5-7
评论： Allen Hammack 2022-5-7
I'm having trouble creating and populating a structure field using a for loop. What I've attempted is
for j = 1:6
structure{1}.file_name_string(j) = strcat('file_name_',num2str(j));
end
which yields
Unable to perform assignment because the indices on the left side are not compatible with the size of the right side.
When I try
for j = 1:length(velocity_raw{1}.velocity_files)
strcat('file_name_',num2str(j))
end
I get the entries that I want, but they aren't assigned to the structure field.
I don't understand what the error message means, and I don't understand how to fix the problem. I expect that my problem is basic, but I just haven't been able to figure it out. Can someone please help?

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采纳的回答

Jonas
Jonas 2022-5-7
编辑：Jonas 2022-5-7
struct are indexed with round brackets, after that use {} if the structure field file_name_string shall be a cell
for j = 1:6
structure(1).file_name_string{j} = strcat('file_name_',num2str(j));
end
this gives you a 1x1 struct with a field which is a cell array of length 6
if you want a 1x6 struct with a field which is ancharacter array, use
for j = 1:6
structure(j).file_name_string = strcat('file_name_',num2str(j));
end
  3 个评论
显示 1更早的评论
Jonas
Jonas 2022-5-7
i dont know, maybe you created a weird variable in your workspace. please type
clear
and try the code again, i have no problems running the code.
Allen Hammack
Allen Hammack 2022-5-7
Thank you! I cleared my variables, and everything works correctly.

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更多回答（1 个）

Steven Lord
Steven Lord 2022-5-7
Ran in:
Do you want the names of the fields in the struct array to be file_name_ followed by a number (file_name_1, file_name_2, etc.)?
s = struct;
for k = 1:5
fn = "file_name_" + k;
s.(fn) = k.^2;
end
s
s = struct with fields:
file_name_1: 1 file_name_2: 4 file_name_3: 9 file_name_4: 16 file_name_5: 25
Or do you want to use actual file names as the field names (something like myImageFile1, myTextFile2, etc.?)
t = struct;
files = {'census.mat', 'eight.tif'};
for k = 1:length(files)
fn = matlab.lang.makeValidName(files{k}); % since field names can't contain periods
t.(fn) = k.^2;
end
t
t = struct with fields:
census_mat: 1 eight_tif: 4
Or do you want to do something else? If so please provide a small concrete example of what you want to do (don't worry about how to create the struct using code, just explain in words.)

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