Array from CSV File

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Megan Stapley
Megan Stapley on 3 Apr 2019
Commented: Walter Roberson on 3 Apr 2019
Hi there,
I have a 4 columns .csv file. I want to create an matrix of only the SECOND And FOURTH columns
How do I do this?
Thanks!

Answers (1)

Walter Roberson
Walter Roberson on 3 Apr 2019
Edited: Walter Roberson on 3 Apr 2019
filename = 'BlackModelTest.csv';
[fid, msg] = fopen(filename, 'rt');
if fid < 0
error('Could not open file "filename" because: "%s"', filename, msg);
end
col2 = {};
col4 = {};
while true
thisline = fgetl(fid);
if ~ischar(thisline); break; end %normal: indicates end of file
if isempty(thisline); continue; end %empty line, including possibly just before end of file
fields = regexp(thisline, ',', 'split');
if length(fields) >= 2
col2{end+1} = fields{2};
end
if length(fields) >= 4
col4{end+1} = fields{4};
end
end
fclose(fid);
temp = str2double(col2);
if ~any(isnan(temp))
col2 = temp; %convert to double if ALL entries can be converted
end
temp = str2double(col4);
if ~any(isnan(temp))
col4 = temp; %convert to double if ALL entries can be converted
end
You will now have variables col2 and col4. If the columns contained only numeric values, then the corresponding variable will be numeric; otherwise it will be a cell array of character vectors. This code does not try to figure out whether there were header lines.
This code does not assume that all lines are complete or that all lines are the same number of fields. Extra fields will be ignored. If the line is too short then the empty array will be at that location.
  7 Comments
Megan Stapley
Megan Stapley on 3 Apr 2019
That outputs a 1 X 42 array
Not a 2 column matrix
Walter Roberson
Walter Roberson on 3 Apr 2019
[col2(:), col4(:)]

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