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Re: read file, given a non-octave header

From: Thomas Treichl
Subject: Re: read file, given a non-octave header
Date: Sat, 27 Jan 2007 14:21:47 +0100
User-agent: Thunderbird (Macintosh/20061207)

the_verge schrieb:
Ok,  One more data loading quesiton:

I am loading a file that has some comment lines preceded by the '#'
character, and then two data description lines, and then the data.  The
first description line is a tab separated list of the variables in the file:

agency_cd       site_no parameter_cd    dd_nu   year_nu month_nu        mean_va

The second line is a list of the number of characters ("s") or numbers ("n")
each column takes up:

5s      15s     5s      3n      4s      2s      12n

Following that, the data is in columns corresponding to the previous two
description lines.
What I want to do is load the data into appropriately named vectors, (some
of the columns are strings, some are numbers) just using the information
from the first two "description lines."  I am doing this a vast number of
times, so automation is necessary (in other words, I can't edit each file by
hand to put it into a certain format).

How do I parse this out?

Hi Vergil,

please next time sent a short (about 5 lines long) example data file, so that nobody needs to create a data file first. My data file is (and I hope yours looks something like that)

  # comment line 1 can be ignored
  # comment line 2 can be ignored
  agency_cd     site_no parameter_cd    dd_nu   year_nu month_nu        mean_va
  5s    15s     5s      3n      4s      2s      12n
  hallo abcde67890abcde world   123     abcd    ab      123456789012
  world 12345abcde12345 hallo   456     efgh    cd      210987654321

And the function you would use could look something like

  function vret = parsedata (filename)
    [vfid, vmsg] = fopen (filename, "r");
    if (isempty (vmsg) == false), error (vmsg); endif

    fgetl (vfid); fgetl (vfid); # Forget about the first two lines
    vcnt = 1;                   # Initialize counter for while loop
    vstr = fgetl (vfid);        # Get third line
    while (vstr != -1)
      [vret{vcnt,1}, vret{vcnt,2}, vret{vcnt,3}, vret{vcnt,4}, \
       vret{vcnt,5}, vret{vcnt,6}, vret{vcnt,7}] = \
          sscanf (vstr, "%s\t%s\t%s\t%s\t%s\t%s\t%s", "C");
      vstr = fgetl (vfid);
      vcnt = vcnt + 1;

    fclose (vfid);

Your return value is of type "cell array of strings" resp. a matrix of cells, so if you need to convert your number strings into real numbers you need to change the above code or write some more.


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