Convert the contents of columns containing numeric text to numbers - matlab

Question

I have a csv file that consists of text or number. But some columns are corrupted as seen in the image below("<<"K.O). When I open the csv file via Matlab (without importing), it converts them to number and define undefined values such as "<<"K.O as NaN as I wanted. But when I read the file via script I wrote:
opts = detectImportOptions(filedir);
table = readtable(filedir,opts);
It reads them as char arrays. Since I have many different csv files (columns are different), I want to do it automatically rather than using textscan(since it requires file format and my file format is different for each csv file). Is there any way to convert the contents of columns containing numeric text to numbers automatically?

Answer 1

As far as I can understand from your comments, this is what you are actually looking for:
for i = 1:numel(files)
file = fullfile(folder,files(i).name));
opts = detectImportOptions(file);
idx = strcmp(opts.VariableNames,'Grade');
if (any(idx))
opts.VariableTypes(idx) = {'double'};
end
tabs(i) = readtable(file,opts);
end

Answer 2

Assuming you have your data stored in a table, you can attempt to convert each column of character arrays to numeric values using str2double. Any values that don't convert to a numeric value (empty entries, words, non-numeric strings, etc.) will be converted to NaN.
Since you want to do the conversions automatically, we'll have to make one key assumption: any column that converts to all NaN values should remain unchanged. In such a case, the data was likely either all non-convertable character arrays, or already numeric. Given that assumption, this generic conversion could be applied to any table T:
for varName = T.Properties.VariableNames
numData = str2double(T.(varName{1}));
if ~all(isnan(numData))
T.(varName{1}) = numData;
end
end
As a test, the following sample data:
T = table((1:5).', {'Y'; 'N'; 'Y'; 'Y'; 'N'}, {'pi'; ''; '1.4e5'; '1'; 'A'});
T =
Var1 Var2 Var3
____ ____ _______
1 'Y' 'pi'
2 'N' ''
3 'Y' '1.4e5'
4 'Y' '1'
5 'N' 'A'
Will be converted to the following by the above code:
T =
Var1 Var2 Var3
____ ____ ______
1 'Y' NaN
2 'N' NaN
3 'Y' 140000
4 'Y' 1
5 'N' NaN