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Jason on 24 Jun 2024 at 14:17
Commented: Jason on 24 Jun 2024 at 14:48
Accepted Answer: Stephen23
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Hi, Im trying to save plot data by using a structured arra
ax=app.UIAxes;
ax.Children;
h1 = findall(ax, 'type', 'line'); % Line objects
nlines=numel(h1);
Assign the desired plot parameters to a struct "S"
for i=1:nlines
thisLine=h1(i);
S(i).Xdata=thisLine.XData; S(i).Ydata=thisLine.YData;
S(i).Colour=thisLine.Color;
S(i).LineStyle=thisLine.LineStyle;
S(i).LineWidth=thisLine.LineWidth;
S(i).DName=thisLine.DisplayName;
end
Save to a .MAT file
try
[file,folder]=uiputfile({'*.mat','Matlab Files'},'Save Data',app.startfolder);
catch
[file,folder]=uiputfile({'*.mat','Matlab Files'},'Save Data','C:\');
end
app.startfolder=folder;
savepath=fullfile(folder,file);
save(savepath,"-struct",'S')
But I keep getting this error:
Error using save
The argument to -STRUCT must be the name of a scalar structure variable.
I have checked the class of S and the fieldnames contained within it:
fields = fieldnames(S)
class(S)
fields =
6×1 cell array
{'Xdata' }
{'Ydata' }
{'Colour' }
{'LineStyle'}
{'LineWidth'}
{'DName' }
ans =
'struct'
Thanks for any help
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Accepted Answer
Stephen23 on 24 Jun 2024 at 14:25
Edited: Stephen23 on 24 Jun 2024 at 14:28
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Explanation: your structure is not scalar: it has nlines elements. The -struct option only works with scalar structures.
Error using save
The argument to -STRUCT must be the name of a scalar structure variable.
% ^^^^^^
Solutions:
- either get rid of the -struct option, or
- create a scalar structure (by making the fields arrays, not the structure).
Tip: always LOAD into an output variable!
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Jason on 24 Jun 2024 at 14:29
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https://www.mathworks.com/matlabcentral/answers/2131476-saving-a-structured-array-containing-plot-parameters-to-a-mat-file#comment_3194546
Edited: Jason on 24 Jun 2024 at 14:33
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Thanks Stephen, so for this option " create a scalar structure (by making the fields arrays, not the structure)", you mean
for i=1:nlines
thisLine=h1(i);
S.Xdata(i)=thisLine.XData; S.Ydata(i)=thisLine.YData;
S.Colour(i)=thisLine.Color;
etc
end
Thanks for tip, but Im not sure I follow.
Thanks
Jason
Steven Lord on 24 Jun 2024 at 14:44
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https://www.mathworks.com/matlabcentral/answers/2131476-saving-a-structured-array-containing-plot-parameters-to-a-mat-file#comment_3194571
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Since several of the properties you're trying to store in the struct are non-scalar, it won't work as you wrote it. But you could have the fields of the scalar struct contain cell arrays, where each cell in the array can have data of different sizes depending on the properties of the specific line you're trying to store inside it.
h = plot(1:10, 1:10, 'r-', 1:7, 10:-1:4, 'k:');
for k = 1:numel(h)
S.XData{k} = h(k).XData;
S.YData{k} = h(k).YData;
end
disp(S)
XData: {[1 2 3 4 5 6 7 8 9 10] [1 2 3 4 5 6 7]} YData: {[1 2 3 4 5 6 7 8 9 10] [10 9 8 7 6 5 4]}
isscalar(S) % yes
ans = logical
1
isstruct(S) % also yes
ans = logical
1
cd(tempdir)
save('mydata.mat', '-struct', 'S')
whos -file mydata.mat
Name Size Bytes Class Attributes XData 1x2 344 cell YData 1x2 344 cell
P = load('mydata.mat')
P = struct with fields:
XData: {[1 2 3 4 5 6 7 8 9 10] [1 2 3 4 5 6 7]} YData: {[1 2 3 4 5 6 7 8 9 10] [10 9 8 7 6 5 4]}
isequal(P, S)
ans = logical
1
Jason on 24 Jun 2024 at 14:48
Direct link to this comment
https://www.mathworks.com/matlabcentral/answers/2131476-saving-a-structured-array-containing-plot-parameters-to-a-mat-file#comment_3194576
Thats fantastic, thankyou!
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