Loading Text File with Multiple sections of headers

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Hi All, I am trying to using the "importdata" command to import to Matlab 2012a from a file that has multiple sections of headers. The file looks like:
header header header
1 1 1
1 1 1
header header header
2 2 2
2 2 2
However, import data will only return the data after the first line of headers (in this example a 2x3 matrix of 1's). How can I get it to also read the data after the second set of headers (so a 4x3 matrix for this example of 1's then 2's). Thank you for the help.
Brendan
  2 Comments
Walter Roberson
Walter Roberson on 8 Jun 2012
Do you know the exact amount of data in each section ahead of time?
Do you want the data broken up into parts, or do you want all the data together?
Does the header always start with the same string?
Brendan
Brendan on 8 Jun 2012
If the data is all in one matrix in matlab that is fine. The headers are four lines but the directly above the data is always the same. And I know the amount of data in each section ahead of time.

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Accepted Answer

Walter Roberson
Walter Roberson on 8 Jun 2012
As you know the amount of data in each section, fopen() the file, and textscan() it section by section, using the 'HeaderLines' option and passing in the count of the number of lines to read.
numlines = 2;
thissectionCell = textscan(fid, '%f%f%f', numlines, 'HeaderLines', 4, 'CollectOutput', 1);
  1 Comment
Brendan
Brendan on 8 Jun 2012
thank you very much. This worked well. I had to call fopen twice to skip over the second group of headers but it got the job done.

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More Answers (1)

per isakson
per isakson on 8 Jun 2012
importdata cannot handle your file.
An approach is to
  1. read the file as characters to a string, buf
  2. split the string, buf, into one string of characters per block of header&data
  3. parse each block with textscan
Something like
function M = Answer( )
fid = fopen( 'cssm.txt', 'r' );
buf = fread( fid, '*char' );
sts = fclose( fid );
while buf > 0
ix2 = first position of next header
str = buf( 1 : ix2-1 );
buf( 1 : ix2-1 ) = [];
cac = textscan( str, format );
peel off the braces
end
end
or write the blocks to separate files and read with importdata.

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