MATLAB: How to Read and plot CSV file and delete infinity values from CSV file

csv readdelete inifinity value from csv fileMATLAB

Hi
I want to read csv file and later plot it by using some formula.
I used csvread, but it doesn’t work as the file contains text (column title) and infinity values which MATLAB read as ∞.
I tried with readtable it can read (c=readtable('sensor.csv');. But again I can’t delete infinity values from the file. When I try with c(isnan(c))=0; or c(~any(isinf(c))) = 0; it always give error
“Undefined function 'isinf' or ‘isnan’ for input arguments of type 'table'”
Can anyone help how to read large csv file (xlsread doesn’t work, file size>1gb) and delete the infinity values which MATLAB read ∞.
Small section of large file is attached sensor.csv
Using Matlab R2017b

Best Answer

Matlab provide many ways to read your csv-files. Here are two variants based on textscan, Read formatted data from text file or string .
sensor.csv contains "???", which I assume is your "infinity value". AFAIK, there is no way to make textscan() or any other reading function directly convert "???" to the numerical value, Inf.
In the script, R1, textscan() converts "???" to NaN and in a second step replaces NaN by Inf. That's fine if the file doesn't have missing values, since they also would be converted to Inf.
In the script, R2, the entire file is read to a character array, chr. Next all '???' are replaced by 'Inf' and finally textscan() parses chr. R2 requires more memory to store chr.
%% R1 
fid = fopen( 'sensor.csv', 'r' );
cac = textscan( fid, '%f%f%f%f%f'                       ...
            ,   'HeaderLines',3, 'CollectOutput',true   ...
            ,   'Delimiter',',', 'TreatAsEmpty','???'   );
[~] = fclose( fid );  
num = cac{1};
% num(isnan(num)) = inf;    % why not just keep the NaNs
num(isnan(num)) = 0;        % or replace NaNs by zero
display( num )
%% R2
chr = fileread( 'sensor.csv' );
% chr = strrep( chr, '???', 'inf' );
chr = strrep( chr, '???', '0' );    % or replace '???' by '0'
cac = textscan( chr, '%f%f%f%f%f'                       ...
            ,   'HeaderLines',3, 'CollectOutput',true   ...
            ,   'Delimiter',','                         );
num = cac{1};
display( num )
Both outputs
num =
            0          Inf       1.8947      0.19107    -0.015871
        4e-06       1.9911       1.9105      0.19107            0
        8e-06       1.9911       1.8947      0.19107            0
      1.2e-05       1.9751       1.9105      0.19107            0
      1.6e-05       1.9911       1.9421      0.17514            0
        2e-05       1.9751       1.9262      0.17514            0
      2.4e-05       1.9911       1.8947      0.17514            0
      2.8e-05       1.9911       1.8947      0.17514            0
      3.2e-05          Inf       1.9105      0.19107     0.015871
      3.6e-05       1.9911       1.9262      0.19107            0
        4e-05       1.9911       1.9105      0.19107            0
      4.4e-05       1.9911       1.9262      0.19107            0
      4.8e-05       1.9911       1.8947      0.19107            0
>>
That's before I realised that you don't want Inf in your matrix.
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