MATLAB: Does the TEXTSCAN function with the ‘treatAsEmpty’ option using ‘NAN’ show an in MATLAB 7.3 (R2006b)

MATLABnantextscantreatasempty

When I use the following code:

textscan(fid,'%s%s%f%f%f%f','delimiter','|','treatAsEmpty','NAN')

MATLAB shows the following error:

 ??? Error using ==> textscan
 TreatAsEmpty strings cannot be numeric.

Best Answer

This is expected behavior in MATLAB. The 'treatAsEmpty' option accepts only string inputs. When the input is of the form 'NAN' or any combination {nan,NAN}, they are treated as NaN(Not a Number). Since NaN has numerical significance, it throws the error “TreatAsEmpty strings cannot be numeric.”

The workaround is to replace all fields that are NAN with NaN and call the textscan function without the 'treatAsEmpty' option, for Example:

textscan(fid,'%s%s%f%f%f%f','delimiter','|');

Related Solutions

MATLAB: Does textscan break when there is a -NaN in the input string or input file

This enhancement has been incorporated in Release 2010a (R2010a). For previous product releases, read below for any possible workarounds:

This is a limitation in the TEXTSCAN function in MATLAB in the way it handles -NaN. As a workaround read -NaN as a string using TEXTSCAN, remove the '-' sign and convert it back to a number. The attached MATLAB file"removeminusnan" demonstrates this conversion. It accepts a filename (that contains numbers including -NaN) and number of columns of numbers as input and produces a matrix output that contains numbers with -NaN replaced by NaN.

Also attached is a sample text file "Nan.txt" that contains numbers in 5 rows and 4 columns. Call the function "removeminusnan" as below to read the numbers, including -NaN, from the text file:

%Nan.txt is the file that contains 4 columns of numbers
removeminusnan('Nan.txt',4)

MATLAB: Doesn’t MATLAB’s “readtable” honor the ‘TreatAsEmpty’ option for some strings in the Excel sheet

As is explained in the documentation for 'readtable' , the 'TreatAsEmpty' option only applies to numeric columns. Since the second column of the sheet contains only string data, the string 'none' is not replaced.As a workaround, the string can be manually replaced with a string 'NaN' using logical indexing :

>> x.Col2(strcmp(x.Col2, 'none')) = {'NaN'}
x = 
    Col1    Col2     Col3
    ____    _____    ____
      5     'abc'    1   
    NaN     'xyz'    2   
      1     'NaN'    3

Note that since this column of the table contains strings (in cells), the entry must be replaced by a cell entry and not an explicit string or numeric value.

In addition to the above, one can also use the "standardizeMissing" function to replace instances of 'none' (across all of the table's variables) with an empty string. The link for the "standardizeMissing" is given below:

http://www.mathworks.com/help/matlab/ref/standardizemissing.html

Alternately, Col2 may usefully be converted to a categorical variable. The 'none' elements can then be turned into undefined elements simply by deleting the 'none' category.

Another way to replace the 'none' elements is to use the standardizeMissing function, which can be used to replace instances of 'none' (across all of the table's variables) with an empty string. This is a more standard way to indicate a missing string value.

Best Answer

Related Solutions

MATLAB: Does textscan break when there is a -NaN in the input string or input file

MATLAB: Doesn’t MATLAB’s “readtable” honor the ‘TreatAsEmpty’ option for some strings in the Excel sheet

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