MATLAB: Read spreadsheet, delete some variables, and save the spreadsheet

MATLAB

I have a spreadsheet 'test.csv' with the columns

date temperature number_of_deadlines

I read this spreadsheet with readtable, then I want to delete the column of 'number_of_deadlines" and then save the spreadsheet 'test2.csv' with

date temperature

Please advise.

Best Answer

Something like this

t = readtable('test.csv');
t.number_of_deadlines = [];
writetable(t, 'test2.csv')

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MATLAB: Remove character from csv file header

You do not need to do that. There some other approaches you can take:

1) readtable() the file as-is. In R2018b at least, that will return a table with 3 variables named Var1, Var2, Var3 -- the original header will be gone . If you need to, you can assign the names to the Properties.VariableNames property of the table

2) Similar to the above, but you also

T = readtable('test.csv');
fid = fopen('test.csv', 'rt');
S = fgetl(fid);
fclose(fid);
varnames = regexp(S, ',', 'split);
varnames( cellfun(@isempty, varnames) ) = [];   %remove any trailing empty fields
T.Properties.VariableNames = matlab.lang.makeUniqueStrings(matlab.lang.makeValidName(varnames));

3) Use textscan() to read the file, either with or without bothering to extract the variable names

4) If you do not need the variable names,

csvread('test.csv', 1, 0)

The 1 tells it to skip 1 row; the 0 tells it to skip zero columns.

MATLAB: Writetable does not replace file

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:

write ten values to a (new?) spreadsheet.
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.
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.

Best Answer

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MATLAB: Remove character from csv file header

MATLAB: Writetable does not replace file

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