Why `WriteMode` isn't working while appending data to xlsx?

I'm doing the following

excelFilename = 'someFile.xlsx';
structFieldnames = fieldnames(myStruct); % <--- where myStruct is your struct of data
for k = 1:length(structFieldnames)
    fieldname = structFieldnames{k};
    writecell(myheaderstruct.(fieldname), excelFilename, 'Sheet', sprintf('%s_matlab', fieldname)); % add header
    writematrix(myStruct.(fieldname), excelFilename, 'Sheet', sprintf('%s_matlab', fieldname),'WriteMode','append');
end

Error:

Invalid parameter name: WriteMode.

If 'WriteMode','append' isn't included, the header is overwritten.

Could someone suggest why `WriteMode` isn't working here?

This is a follow up to my previous post here.

This

writematrix(data.(fieldname), excelFilename,'-append', 'Sheet', sprintf('%s_simgraph', fieldname));

also doesn't work.

Wrong number of arguments. A filename must be provided when supplying additional parameters, and each parameter name must be followed by a value.

I'm using 2109b.

Answer 1

[Walter Roberson]

https://www.mathworks.com/help/matlab/release-notes.html?rntext=&startrelease=R2020a&endrelease=R2020a&groupby=release&sortby=descending&searchHighlight=

Writemode is a new option as of R2020a.

[Deepa Maheshvare]

Could you please suggest what can be done to append data to an existing sheet in the previous versions?

[Walter Roberson]

Read the existing sheet as cell. Pad it or the new data to have the same number of columns. Put the two parts together. Write out to the sheet.

[Anthony Phipps]

This post is a life saver - thanks