MATLAB: Writetable does not replace file

MATLABwritetable

Hi,
I just observed a somewhat confusing behaviour with the writetable function in matlab. Here is a simple code to explain it
t = T(1:10,:)
writetable(t, '/tmp/test.xlsx')
writetable(t, '/tmp/test1.xlsx')
t = t([2 4 1 3 5],:)
writetable(t, '/tmp/test.xlsx')
writetable(t, '/tmp/test2.xlsx')
now test2.xlsx is a table with 5 rows, as expected.
test.xlsx is a table with 10 rows, wheres the first 5 equal test2.xlsx and the last 5 equal test1.xlsx
I would expect test.xlsx should be the same as test2.xlsx. I had a misunderstanding in a collaboration with colleagues which was close to publish erroneous data.
I there a way to change this?
I'm using matlab on ubuntu 18.04 with libreoffice.
Thanks for any help
Dom

Best Answer

According to the writetable help, "If filename is the name of an existing spreadsheet file, then writetable writes a table to the specified location, but does not overwrite any values outside that range", and that is exactly what you are observing:
  1. write ten values to a (new?) spreadsheet.
  2. write five values to a (now already existing) spreadsheet. According to the documentation this will add those five values to the default location, as in your code and leave all other existing values unchanged.
  3. thus you still see five of the values from step 1. (the ones not overwritten by step 2.), and five values from step 2..
So far it seems to be behaving as described in the documentation.
While this might be useful in some situations clearly in other cases (like yours) it would be useful to delete any existing content before writing the new content, but there does not currently seem to be an option for this. I suggest that you make an enhancement request (with a link to this thread), as I am sure that others would also find this a useful option.
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