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How to Fix "Warning: Colon operands must be real scalars" Warning

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Burhan Burak
Burhan Burak 2024-4-7
回答： Nieves about 18 hours 前
When I run the code below, it works as I wanted, but I get a warning. I tried different things to fix it, but of no avail. How can I refactor my code so that I will not face any related issue as the warning states if I can?
ply_nums_range = [4, 8, 16, 32, 64];
x = rand(1, 2);
data = cartesian_product({b_range, ...
N_xx_range, ...
N_yy_range, ...
N_xy_range, ...
ang_range});
for e = ply_nums_range
ply_nums = e;
for i = 1:length(data)
b = data(i, 1);
N_xx = data(i, 2);
N_yy = data(i, 3);
N_xy = data(i, 4);
ang = data(i, 5);
iteration = [a, ...
b, ...
N_xx, ...
N_yy, ...
N_xy, ...
[PLY_ANGS(ang, x), flip(PLY_ANGS(ang, x))]];
thetas = cell(1, ply_nums);
for j = 1:ply_nums
thetas{j} = sprintf("theta_%d", j);
end
variable_names = ["a", "b", "N_xx", "N_yy", "N_xy", thetas];
table_data = array2table(iteration, ...
'VariableNames', ...
variable_names);
sheet_name = sprintf("%d_ply_case", e);
writetable(table_data, ...
"design-cases/case.xlsx", ...
'WriteMode', 'Append', ...
'Sheet', sheet_name);
end
end
Console output:
Warning: Colon operands must be real scalars. This warning will become an error in a future release.
> In matlab.io.spreadsheet.internal.write.writeXLSFile>getRangeToWrite (line 575)
In matlab.io.spreadsheet.internal.write.writeXLSFile (line 262)
In writetable (line 426)
In test_case (line 72)
  2 个评论
Walter Roberson
Walter Roberson 2024-4-7
there is something odd about the way it is interpreting the sheet parameter. Please verify that sheet_name contains a valid character vector. Experiment with moving the numeric part of the character vector to the end.

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回答（5 个）

Jakob Weis
Jakob Weis 2024-4-23
In my case the warning was triggered because the colon operands were indexed with for-loop indices which I accidentally parsed as a column rather than a row vector.
for_indices = (1:10)'; % Column vector parsed as for-indices triggers warning.
X = 1:10;
Y = 101:110;
for i = for_indices
R = X(i):Y(1);
end
It doesn't look like this is the issue OP is facing but I thought I'd mention it in case somebody else comes across this thread.
Ryan Lamb
Ryan Lamb 2024-6-12
编辑：Ryan Lamb 2024-6-12
I think the Warning is coming from the 'WriteMode' being set to 'Append'.
I get the same warning any time I append to a row greater than 10.
VBBV
VBBV 2024-4-7
for k = 1:numel(ply_nums_range)
ply_nums = ply_nums_range(k); %
for i = 1:length(data)
b = data(i, 1);
N_xx = data(i, 2);
N_yy = data(i, 3);
N_xy = data(i, 4);
ang = data(i, 5);
iteration = [a, ...
b, ...
N_xx, ...
N_yy, ...
N_xy, ...
[PLY_ANGS(ang, x), flip(PLY_ANGS(ang, x))]];
thetas = cell(1, ply_nums);
for j = 1:ply_nums % scalar limit
thetas{j} = sprintf("theta_%d", j);
end
variable_names = ["a", "b", "N_xx", "N_yy", "N_xy", thetas];
table_data = array2table(iteration, ...
'VariableNames', ...
variable_names);
sheet_name = sprintf("%d_ply_case", ply_nums);
writetable(table_data, ...
"design-cases/case.xlsx", ...
'WriteMode', 'Append', ...
'Sheet', sheet_name);
end
end
  9 个评论
显示 7更早的评论
VBBV
VBBV 2024-4-8
Ran in:
Though sheetname has no issues, but it may also be the cause, try to give sheetname that begins with character instead of number
sheet_name = sprintf("ply_case_%d", 4)
sheet_name = "ply_case_4"
Burhan Burak
Burhan Burak 2024-4-8
编辑：Burhan Burak 2024-4-8
Yes, "design-case" is an existing folder in the current folder along with the file I run so backward slash use in designating relative file path gives me an error. Also I tried the alternative sheet name scheme as you and the other user pointed out, and still get the same warning. Additionally, it is worth mentioning something I noticed in the created case.xlsx file when I look over it. I attach a related image of it below. After some column it does not write in values as expected.

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Steven Lord
Steven Lord 2024-4-9
If you have a small case with which you can reproduce this behavior, could you please send it to Technical Support directly using this link? Or could you attach to this Answers post (or send it to Support) a small MAT-file with a representative table_data table array that reproduces this behavior when you run this writetable command? I'd like for us to investigate why writetable is issuing this warning message.
writetable(table_data, ...
"design-cases/case.xlsx", ...
'WriteMode', 'Append', ...
'Sheet', sheet_name);
  1 个评论
Burhan Burak
Burhan Burak 2024-4-9
I edited said .m file for minimally reproducible example of the warning, and you can find it appended to this message. I hope this helps.

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Nieves
Nieves about 18 hours 前
I'm getting this same error, with both writetable and writematrix. My sheet names have no digits:
writetable(toWrite,fullfile(outDir,specName),'Sheet','Spectral_Data','WriteMode','Append')
writematrix(nemList,fullfile(outDir,specName1),'Sheet','FileNames','WriteMode','Append')
This error has only appeared since updating to R2024a.

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