RE: reading data using fgets in while loop

[PhilipNienhuis]

newbie_octave wrote
> 
>> Date: Mon, 12 Mar 2012 10:17:32 -0700
>> From: pr.nienhuis@
>> To: help-octave@
>> Subject: Re: reading data using fgets in while loop
>> 
>> 
>> 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 help@
>> > 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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> 
> thanks Philip,
> ...I realize that I don't have textread.m in my io folder. can you tell me
> where can I download it.
> Bobby
>  

What Octave version on what operating system are we talking about?

I showed how to use textread() with Octave v.3.6.1; in 3.6.0 textread was
significantly improved.

If your Octave version is not too old (should be >= 3.4.0) you might
download textread.m + the required companion file strread.m here:
  http://hg.savannah.gnu.org/hgweb/octave/file/05635e4c605a/scripts/io
and replace the ones on your hard disk in 
  ./share/octave/<version>/m/io
(You'll have to search a bit where this exactly is, I don't know my way
around on your PC)

If you run an older Octave version (3.2.4 on Windows?) you're strongly
advised to upgrade a.s.a.p.

Philip

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