Converting Categorical Array/Table to Numerical
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Hello!
I have a 23000x4 set of data that is a table (called temp). It is all numbers except for the times data was missing it was filled in with 'NA', therefore the table is categorial. I am looking to change it to a numerical and have all the 'NA' changed to 'NaN' so I can run max and min and those kinds of things on it without running into issues. Thank you for the help!
12 Comments
Adam Danz
on 10 Jun 2020
What function did you use to import it? You can control the class of the data you're importing. A csv file doesn't control that for numeric values.
Accepted Answer
Adam Danz
on 10 Jun 2020
Edited: Adam Danz
on 23 Sep 2022
By far the best solution is to avoid representing numeric values as categorical values in the first place. If you can un-do that, that's the best solution.
If that cannot be done, here's how to convert categorical values that contain numeric values in a table.
Table T can contain mixed classes (some classes may cause errors).
This demo detects which columns of T contains values that can be converted to numers. It then creates an output table T_converted that contains the num-categorical-number columns of T and the categorical-number columns converted to numbers.
% Create demo table with a mix of stings, categorical numerals, and numbers
T = table(["A";"B";"C";"D";"E"], ...
categorical(randi(10,5,1)), ...
randi(10,5,1), ...
categorical(randi(10,5,1)), ...
'VariableNames', {'A','B','C','D'})
varfun(@class, T)
% Determine which columns are categoricals
% NOTE: This assumes you want to convert all categorical table variables
% to numeric. Otherwise, additional column indexing will be needed.
iscat = varfun(@iscategorical, T,'OutputFormat','Uniform');
% Convert the categorical table variables to numeric
Tnum = array2table(str2double(string(T{:,iscat})), ...
'VariableNames', T.Properties.VariableNames(iscat));
% Create an updated table with the converted data and maintain
% original column order
T_converted = [T(:, ~iscat), Tnum];
[~,colorder] = ismember(T_converted.Properties.VariableNames, T.Properties.VariableNames);
T_converted(:,colorder)
varfun(@class, T_converted)
This answer was corrected on 9/23/22; thanks to Ahmed Rady for pointing out the problem
2 Comments
Ahmed Rady
on 23 Sep 2022
Edited: Ahmed Rady
on 23 Sep 2022
Hi Adam
Thanks for the code
But it seems that the numeric values in the original table were transformed.
I thought the aim is to only change the catergorical variables.
Adam Danz
on 23 Sep 2022
My previous answer involved applying double() to the categorical-numbers which converts the categoricals into a grouping number rather than the numbers represented within the categories.
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