Re: reading data using fgets in while loop

[indium]

> > Date: Mon, 12 Mar 2012 11:37:37 +0000
> > From: address@hidden
> > To: address@hidden
> > CC: address@hidden
> > Subject: Re: reading data using fgets in while loop
> > 
> > On Sun, Mar 11, 2012 at 04:00:36PM -0700, 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!
> > > 
> > > 
> > > 
> > > --
> > > View this message in context: 
> > > http://octave.1599824.n4.nabble.com/reading-data-using-fgets-in-while-loop-tp4464844p4464844.html
> > > Sent from the Octave - General mailing list archive at Nabble.com.
> > 
> > Hi, 
> > I would try while(!eof(fid)) instead of while(1). 
> > This would stop the while loop when the whole file is read. 
> > 
> > as an example, I've copied a part of a script that I use myself. This also 
> > does some date conversion to 'seconds since epoch'. 
> > To read the manual, do 'doc eof' or 'doc mktime', etc.
> > 
> > ------------------------------------------------
> > params27C.date:
> > 05/12/11 18:56:37 0.001728386 16.43405 1.323835
> > 05/12/11 19:26:39 0.001676934 16.41423 1.334429
> > 05/12/11 19:56:40 0.001599179 16.40604 1.351362
> > 05/12/11 20:54:10 0.001547091 16.35170 1.361025
> > ------------------------------------------------
> > 
> > script:
> > 
> > pos27f=fopen('./fits2012/27C/params27C.date');
> > n=0;
> > while (!feof(pos27f))
> >         n++
> >         line=strsplit(fgetl(pos27f),' ')
> >         datestring=sprintf('%s %s',line{1},line{2});
> >         pos27sec(n)=mktime(strptime(datestring,'%d/%m/%y %T'));
> >         pos27(n)=str2num(line{4});
> > endwhile
> > fclose(pos27f)
> > 
> > 
>                                         

On Mon, Mar 12, 2012 at 11:23:56AM -0400, financial engineer wrote:
> 
> 
> Thanks for the script...I rewrote mine as follows:
> fname="/tmp/VIXts.csv"
> fid = fopen(fname);
> n=0;
> while (!feof(fid))
> n++
> tline=strsplit(fgetl(fid),',')
> datestring=sprintf('%s',tline{1});
> fid(n)=str2num(tline{3});
> endwhile
> fclose(fid)
> 
> but when it encounters endwhile, it gives the following error:
> > endwhile
> error: feof: invalid stream number = -1
> 
> 

Dear financial engineer,

please put your 'reply-text' at the bottom of the thread (like I do here), so 
that the thread is readable from top-to-bottom.

feof() complains because the fid is not a positive number. The fid is not 
positive, which most certainly means that the file
was never opened. For instance, the file doesn't exist, the name or directory 
is spelled wrong, the file permission on the filesystem is
wrong, etc, etc. 

Can you try to do it manually, step by step, by starting typing the commands on 
the octave command-line?
Try other files, skip the while() loop in first instance, check the file name, 
try fid=fopen('/tmp/VIXts.csv') directly, etc, etc.