Re: reading data using fgets in while loop

[PhilipNienhuis]

newbie_octave wrote
> 
> I have a .csv file with the following data
> 
> 01/03/2012,H (Mar 12),26.750000,2584
> 01/04/2012,H (Mar 12),26.280000,2330
> 01/05/2012,H (Mar 12),26.000000,3198
> 01/06/2012,H (Mar 12),25.500000,3045
> 01/09/2012,H (Mar 12),25.350000,2314
> 01/10/2012,H (Mar 12),25.050000,2685
> 
> and I am a newbie to octave. I ran the following command to read the above
> data into octave
> 
> X=csvread("/tmp/hist.csv")
> 
> but it returns the following matrix.
> 
> 1.0000e+00   0.0000e+00   2.6750e+01   2.5840e+03
>    1.0000e+00   0.0000e+00   2.6280e+01   2.3300e+03
>    1.0000e+00   0.0000e+00   2.6000e+01   3.1980e+03
>    1.0000e+00   0.0000e+00   2.5500e+01   3.0450e+03
>    1.0000e+00   0.0000e+00   2.5350e+01   2.3140e+03
>   1.0000e+00   0.0000e+00   2.5050e+01   2.6850e+03
> 
> 
> Obviously, it is not reading the text correctly
> so I am now using fgets() as follows:
> 
> fid=fopen(fname);
> fout="out.mat"
> global tline;
> global tempstr;
> while 1
> tline = fgets(fid);
> sep=",";
> tempstr=strsplit(tline, sep);
> dt=tempstr(1);
> cname=tempstr(2);
> price=str2double(tempstr(3));
> volume=str2double(tempstr(4));
> if ~ischar(tline), break,end;
> end
> disp(tline);
> fclose(fid);
> 
> but when I run the script, it returns -1 due to disp(tline) being after
> the end. I want to be able to compute the volume-weighted average price,
> and not have to do it all within the script that reads the data from the
> file. But, given that I cannot access any of the variables outside the
> while loop, I am stuck. Ideally, I could have used csvread() or dlmread()
> but that is messing up the string fields in my file. Can anyone please
> suggest how I fix this so I can manipulate the variables outside the while
> loop that gets the data from the .csv file. thanks!
> 
> I also get the following error in using strsplit, and I don't understand
> what mistake I am making as I am following the usage guidelines. I tried
> split, but I am advised to use strsplit. 
> octave-3.2.4:110> strsplit(tline,sep)
> error: Invalid call to strsplit.  Correct usage is:
> 
>  -- Function File: [S] = strsplit (P, SEP, STRIP_EMPTY)
> 
> 
> Additional help for built-in functions and operators is
> available in the on-line version of the manual.  Use the command
> `doc <topic>' to search the manual index.
> 
> Help and information about Octave is also available on the WWW
> at http://www.octave.org and via the address@hidden
> mailing list.
> 

There are a few more text reading functions that may help out.
E.g., textread:
(applied to your data in a file txt.csv)

octave-3.6.1.exe:2> [a, b, c, d] = textread ('tst.csv', "%s %s %f %d",
"delimiter", ",")
a =
{
  [1,1] = 01/03/2012
  [2,1] = 01/04/2012
  [3,1] = 01/05/2012
  [4,1] = 01/06/2012
  [5,1] = 01/09/2012
  [6,1] = 01/10/2012
}
b =
{
  [1,1] = H (Mar 12)
  [2,1] = H (Mar 12)
  [3,1] = H (Mar 12)
  [4,1] = H (Mar 12)
  [5,1] = H (Mar 12)
  [6,1] = H (Mar 12)
}
c =

   26.750
   26.280
   26.000
   25.500
   25.350
   25.050

d =

  2584
  2330
  3198
  3045
  2314
  2685

With some postprocessing (e.g., datenum (a, "dd/mm/yyyy") )  you can get any
output you want.

Philip


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