MATLAB: Replace String with a NaN in table

badMATLABnanstringtable

Hey guys!

I am challenged with a table, consisting various numbers and a few "'Bad'" cells. I guess they are strings. My goal now is to replace these "Bads" with NaNs.

How do I achieve that the easiest way?

Best regards, Spacey

Best Answer

It sounds like you imported a file where some of the columns were mostly numbers, but some strings mixed in. Best to avoid getting into the corner that you're in. You might have been able to explicitly say that the column is numeric. You might have been able to use the TreatAsEmpty parameter to readtable (if that's what you used).

Otherwise, if you have variables in the table that are cell arrays but that you want to be numeric, you might need to do one of a couple different things. In general, you need to put numeric things in all the cells and then concatenate the contents to get a numeric vector, but first you'll need to describe exactly what you have.

Related Solutions

MATLAB: Existing table, populate a column with string (receiving errors)

You are close, but you are trying to assign a character vector to a double variable (NaN = not a number). You can see that if you run the command summary(mytable).

You also do not need to put the text into a cell if you use the string data type.

See if you can get this code to work for your needs.

myArray = nan(5,2)
mytable = array2table(myArray);
mytable.Properties.VariableNames = {'colA', 'colB'};
mytable2 = convertvars(mytable,"colB",'string');
mytable2.colA(:) = 459;
mytable2.colB(:) = "words"

You say you have a lot of data. If the variables already exist, you could do something like this:

colA = nan(5,1);
colB = strings(5,1);
mytable = table(colA,colB);
mytable.colA(:) = 459; % just a random number, proof-of-concept that it works
mytable.colB(:) = "words" % this throws errors

MATLAB: Merge tables with different dimensions

tables like matrices must have the same number of columns (variables with regards to tables) to concatenate them vertically. In addition, for tables, the variable names must be identical.

You can of course add variables to either table until all the variable names match:

t1 = array2table(magic(5), 'VariableNames', {'a', 'k', 'o', 'p', 'w'});
t2 = array2table(magic(6), 'VariableNames', {'a', 'p', 'o', 'v', 's', 'k'});
t1colmissing = setdiff(t2.Properties.VariableNames, t1.Properties.VariableNames);
t2colmissing = setdiff(t1.Properties.VariableNames, t2.Properties.VariableNames);
t1 = [t1 array2table(nan(height(t1), numel(t1colmissing)), 'VariableNames', t1colmissing)];
t2 = [t2 array2table(nan(height(t2), numel(t2colmissing)), 'VariableNames', t2colmissing)];
t = [t1; t2]

Best Answer

Related Solutions

MATLAB: Existing table, populate a column with string (receiving errors)

MATLAB: Merge tables with different dimensions

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