Export data to specified excel rows using writematrix

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Hi,
I am trying to export data to some rows in excel. Here is an example:
writematrix(subjects,'Matlab to Excel Subject Data.xlsx','Sheet',2,'Range','B3:I3')
I have tried using 'WriteMode' and 'append' however, this overrides my headings and titles in the excel file. I would like to fill B3:I3 and continute to B40:I40. I have tried using a for loop which will increase the row by 1.
Here is what I tried:
for i = 3:40
writematrix(subjects,'Matlab to Excel Subject Data.xlsx','Sheet',2,'Range','B',(i+1),':I'(i+1))
end
Unforetunely this does not work. Is there a solution to this?
  10 Comments
Voss
Voss on 13 Feb 2022
Since randn(1,8) works, I guess the thing to do would be to make sure the variable subjects has the values you expect right before you write it to file. It looks like maybe the value of subjects is set by the script Master_File, so you might set a breakpoint in there where subjects is set, and/or a breakpoint on the writematrix() line so you can check the value of subjects right before it goes to file.
Cassandra Martin
Cassandra Martin on 14 Feb 2022
Thank you for all of your help. I've decided it will be best to create one giant matrix and then export it to excel using this method: 'Range','B3:I40'

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Accepted Answer

Jeremy Hughes
Jeremy Hughes on 14 Feb 2022
I believe it should be possible to do this using (almost) the syntax you tried, and there are some suggestions in the comments, but I wanted to share the "WriteMode" parameter as that should do exactly what you're looking for.
for i = 1:5
writematrix(randn(1,3),'test.xlsx','WriteMode','append');
end
A = readmatrix('test.xlsx')
A = 5×3
0.1677 1.1237 1.0494 -1.1193 -0.3099 -0.5449 -1.1076 1.6841 -0.0993 -2.1830 -0.7395 0.7467 -1.0709 0.0737 0.2002
That said, it's going to be a lot slower writing single rows at a time, since writematrix has to open, write, and close the file each time. It's not meant for incremental writing. So the solution to build up the matrix first makes the most sense to me.
The append appoach could be useful if you have very large arrays, but I suspect that the XLSX format will limit you before the array size will.

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