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
0 Comments
Accepted Answer
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
Walter Roberson
on 20 Sep 2017
readtable() delegates to textscan() which does not need spaces between the % format elements.
More Answers (1)
Cedric
on 20 Sep 2017
Edited: Cedric
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
on 21 Sep 2017
Edited: Cedric
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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