HELP!! Extract from multiple .csv (in table format) the column number 10

I WANT TO EXTRACT FROM MULTIPLE .CSV THE COLUMN (NUMBER 10) WITH THE NAME 'KEYRESPONSE2CORR'

I RECEIVE AN ERROR, WHY?

param='keyResponse2corr'; %Change default prameter name with required parameter
%% select folder
dataFolder = uigetdir();
filePattern = fullfile(dataFolder, '*.csv');
list = dir(filePattern);

Output = table();
for kk = 1:numel(list)
    filename = list(kk).name;
    data     = readtable(fullfile(list(kk).folder, filename));
    try
        [~, varname] = fileparts(filename);  % remove the file extension
        Output.(varname) = data.(param);
    catch ME
        fprintf('Cannot find [%s] in file: %s\n  %s', ...
            param, filename, ME.message);
    end
end

ERROR:

Cannot find [keyResponse2corr] in file: Jan_14_1131.csv
  Unrecognized variable name 'keyResponse2corr'

Answer 1

[Chien-Han Su]

I assume that you already check the file 'Jan_14_1131.csv' and make sure there is a parameter 'keyResponse2corr' in the csv file.

It seems that the error message you got is directly generated from the catch block, so you may have a bug in the try block. The bug is resulted from the mismatch of number of input argument for function 'fileparts', I suggest you try to replace

[~, varname] = fileparts(filename);  % remove the file extension

with

[~, varname,~] = fileparts(filename);  % remove the file extension

and see if this works for you.

[Myke Ziz]

Hi thank you a lot for your fast answer!!

Unfortunately I still get an error.

I add a picture of the table Matlab is reading.

Cannot find [keyResponse2_corr] in file: ....

[Walter Roberson]

When the error occurs, what shows up for

data.Properties.VariableNames

[Myke Ziz]

Hi Robert,

it shows as if they were cell arrays, should I change the table format?

[Walter Roberson]

You have

        Output.(varname) = data.(param);

That can also fail if varname is not a valid table variable name. In particular, until R2019b, the names had to be valid MATLAB variable names; it was not until R2019b that they added the ability to use arbitrary character vectors as table variable names.

[Myke Ziz]

How should I correct the error then?

Use another Matlab version?

Thank you a lot for your help!!

I am currently using the matlab 2018b

[Walter Roberson]

After your line

[~, varname] = fileparts(filename);  % remove the file extension

(which is fine by itself, you do not need the extra ~ output) add

varname = genvarname(varname, fieldnames(Output));

This will modify the file name into something that is a valid variable name and that is different from all of the other names generated so far.

However, the result might not be all that readable. For example in a test I did just now, some of the generated names included

    {'ishg2'                                                          }
    {'jbigkit0x2D20x2E10x2Etar'                                       }
    {'jgdsens0x2Dpa0x2Dwavplay0x2D46c387a'                            }
    {'joe0x2Dof0x2Dall0x2Dtrades0x2Dxml2struct0x2D91c3b8a'            }
    {'johnyf0x2Dfig2u3d0x2Dv10x2E00x2E10x2D20x2Dg74fe75d'             }
    {'jpeg_toolbox'                                                   }

Field names such as 'johnyf0x2Dfig2u3d0x2Dv10x2E00x2E10x2D20x2Dg74fe75d' (which was originally 'johnyf-fig2u3d-v1.0.1-2-g74fe75d') are essentially unreadable messes to humans, and the uniqueness requirements imply that you cannot predict the new name given just the original name alone. You should be reconsidering using the file names as field names for your struct. Consider using a cell array in which one column is the table and the other column is the file name.

[Myke Ziz]

Thank you so much Walter!!

Very helpful!!

It worked!!

I wish you a nice evening and thank you again for all the advices!!

[Walter Roberson]

For multiple parameters:

params = {'keyResponse2corr', 'keyResponse2false'};

%% select folder
dataFolder = uigetdir();
filePattern = fullfile(dataFolder, '*.csv');
list = dir(filePattern);
Output = table();
for kk = 1:numel(list)
    filename = list(kk).name;
    data     = readtable(fullfile(list(kk).folder, filename));
    try
       for P = params
          thisvar = P{1};
          Output.(thisvar){kk} = data.(thisvar);
       end
    catch ME
         fprintf('Cannot find [%s] in file: %s\n  %s', ...
            thisvar, filename, ME.message);
    end
    Output.Filename{kk} = filename;
end

... If you are going to use a table() then you might as well use a table. The organization you were using was more suitable for using a struct() rather than a table()