MATLAB: Is MATLAB unable to read an ASCII file containing a large amount of data in a single line using the CSVREAD function

csvreadfilehangsi/olineslongMATLABmemorytime

Why is MATLAB unable to read an ASCII file containing a large amount of data in a single line using the CSVREAD function?

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This bug has been fixed in Release 14 Service Pack 2 (R14SP2). For previous releases, please read below for any possible workarounds:

This has been verified as a bug in MATLAB in the way that the CSVREAD function handles large data files.

Currently, as a workaround, try the following code:

fid = fopen('filename'); 
a = textscan(fid,'%n','delimiter',',');

This reads the file rather quickly and creates an array of doubles. The difference is that when CVSREAD reads the same file, it tries to have a format string with thousands of fields, one for each line of data.

Related Solutions

MATLAB: Csvread file containing text

The solution is very simple: use textscan instead. textscan works with files containing mixed (numeric and text) data, whereas the functions csvread and dlmread only read numeric data.

When you have this kind of task it is easy to browse the help documentation and find all of the file reading/writing functions listed:

http://www.mathworks.com/help/matlab/text-files.html

and then you can read their descriptions, and pick the best one for your task.

MATLAB: Csvread without decimal point

But it is the input data...you're ignoring the scale factor Matlab uses when display disparate values on the command window...

>> type sepp.csv
17,1413736800061,4,2
17,1413736800153,12,0
17,1413736800239,6,2
17,1413736800324,5,1
17,1413736800410,6,1
17,1413736800496,6,1
>> csvread('sepp.csv')
ans =
 1.0e+12 *
  0.0000    1.4137    0.0000    0.0000
  0.0000    1.4137    0.0000         0
  0.0000    1.4137    0.0000    0.0000
  0.0000    1.4137    0.0000    0.0000
  0.0000    1.4137    0.0000    0.0000
  0.0000    1.4137    0.0000    0.0000
>> [ans(:,1) ans(:,3)]
ans =
  17     4
  17    12
  17     6
  17     5
  17     6
  17     6
>>

NB: the 1.0e+12 * in the beginning of the array after reading the file; it's significant.

To see the values are really there, then displayed the first and third columns so the scaling is unity.

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MATLAB: Csvread file containing text

MATLAB: Csvread without decimal point

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