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

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

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Cam Salzberger 2017-9-20

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What many of the built-in file parsing functions do is go into the file and try to determine the structure of it from the first few lines. Then it tries to read the whole file using that structure. In the case of failure, it may try a couple of other ways as well.

Since this depends on the data being consistent throughout the file, which yours isn't, the data isn't being read correctly. You could write your own code that checks every line of the file to see which is the longest, and then parses the whole file in that way. It would essentially double the amount of time needed to read the file, but it's doable.

Or, if you know your expected file structure exactly, then just programmatically create your format string, as Walter suggested. Although you'd probably want a space or tab in there:

formatStr = repmat('%f\t', 1, 100);

More ideally, you would modify whatever it is that is creating the files to put something in the missing areas, rather than leaving them blank. Then you can use the TreatAsEmpty specifier to mark those values uniformly. But this isn't always an option.

Walter Roberson 2017-9-20

readtable() delegates to textscan() which does not need spaces between the % format elements.

Jeppe Sørensen 2017-9-21

By converting NaN to zeros after importing, this works excellently for me. Thank you!

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Answer 2

Cedric 2017-9-20

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https://ww2.mathworks.cn/matlabcentral/answers/357377-how-to-import-data-from-a-non-symmetric-txt-file#answer_282421

编辑：Cedric 2017-9-20

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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.

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Jeppe Sørensen 2017-9-21

This works as intended as well, and is a very good answer. Thank you for this. Cam Salzburgs answer gets accepted, however, as it is a bit simpler.

Cedric 2017-9-21

编辑：Cedric 2017-9-21

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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