How to import data from a non-symmetric .txt file.

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We have the following data file:
1
2 3
5 6 7
How can I import that into MATLAB easily, so the empty block become zero? Like this:
1 0 0
2 3 0
4 5 6
load does not work and importdata gives:
1 NaN
2 3
4 5
6 NaN

Accepted Answer

Cam Salzberger
Cam Salzberger on 19 Sep 2017
Hello Jeppe,
If you give an explicit format to use, the data read functions will try to stick to it as best as possible. My personal preferred data read function is readtable. Just tell it not to assume there are header lines (which is probably why it's skipping the "1" by default), and read using your desired format:
t = readtable('datafile.txt','ReadVariableNames',false,'HeaderLines',0,'Format','%f %f %f');
-Cam
  5 Comments
Jeppe Sørensen
Jeppe Sørensen on 21 Sep 2017
By converting NaN to zeros after importing, this works excellently for me. Thank you!

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More Answers (1)

Cedric Wannaz
Cedric Wannaz on 20 Sep 2017
Edited: Cedric Wannaz on 20 Sep 2017
If you are stuck with usual tools, try this:
content = fileread( 'virusDat.txt' ) ;
% - Split in rows, remove extra empty ones.
data = strsplit( content, '\n' ) ;
while isempty( data{end} )
data(end) = [] ;
end
% - Convert to numeric and get max number of columns.
data = cellfun( @(x) sscanf( x, '%d' ), data, 'UniformOutput', false ) ;
nCols = max( cellfun( @numel, data )) ;
% - Define padding function and pad with e.g. NaNs.
pad_fun = @(x) [reshape( x, 1, [] ), repelem( NaN, 1, nCols-numel( x ))] ;
data = cellfun( pad_fun, data, 'UniformOutput', false ) ;
% - Concatenate padded rows.
data = vertcat( data{:} ) ;
EDIT : replaced
nCols = numel( data{end} ) ;
with
nCols = max( cellfun( @numel, data )) ;
in case you don't always have this pyramidal structure.
  2 Comments
Cedric Wannaz
Cedric Wannaz on 21 Sep 2017
Edited: Cedric Wannaz on 21 Sep 2017
My pleasure! It was just to give you an alternate approach for dealing with "unorthodox" files. Note that it doesn't require that you hard-code 24 for defining a format string and that it is faster than READTABLE, essentially because of the detection of options in READTABLE for importing that takes time.

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