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Import text file with blank lines. Matlab not replacing them with NaN

Asked by mashtine on 29 Jan 2015
Latest activity Edited by per isakson
on 30 Jan 2015
Matlab is not replacing my blank lines in my txt file with NaN but just joins all the data together. Unfortunately I need to data in the exact order it is as each line is a unique timestamp but the times are do not come in the txt file.
Any ideas? Tried importdata and textscan with no luck. Using R2014b

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1 Answer

Answer by per isakson
on 29 Jan 2015
Edited by per isakson
on 30 Jan 2015
 Accepted Answer

Remains (at least) two possibilities
  • a loop over fgetl
  • read the file as one string, replace empty lines by 'nan nan ... ' and parse with textscan
Example (R2013a)
>> cac = cssm;
>> cac{:}
ans =
16 2 3 13
5 11 10 8
NaN NaN NaN NaN
9 7 6 12
4 14 15 1
where
function cac = cssm
str = fileread('cssm.txt');
str = regexprep( str, '(?<=\r?\n)[ ]*(?=\r?\n)', 'nan nan nan nan');
cac = textscan( str, '%f%f%f%f', 'CollectOutput', true );
end
and where cssm.txt contains
16 2 3 13
5 11 10 8
9 7 6 12
4 14 15 1
&nbsp
Replace
str = regexprep( str, '(?<=\r?\n)[ ]*(?=\r?\n)', 'nan nan nan nan');
by
str = regexprep( str, '(?<=\r?\n)[ ]*(?=\r?\n)' ...
, 'nan nan nan nan', 'emptymatch' );
to handle empty lines

  10 Comments

Hi Per,
Thank you for all the illustrations, I agree with all of your conclusions! After spending quite a bit of time working on alternate approaches based on tokens (which happens to be a little bit slower ultimately), I just realize that we don't need to match the eventual \r in the look behind.
Hi Cedric,
You are right, "\r" is not needed in the "look behind". And possibly, it saves on execution time to exclude it.

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