RE: reading data using fgets in while loop

[financial engineer]

> Date: Mon, 12 Mar 2012 15:48:40 +0000
> From: address@hidden
> To: address@hidden
> CC: address@hidden
> Subject: Re: reading data using fgets in while loop
>
> > > 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.

hi Indium,
In fact the file was missing, so now it is capturing the price and volume, but I only get one date. To fix that I tried, using datestring(n) as below:

here is my updated code:
fname="/tmp/VIXts.csv"
fid = fopen(fname);
n=0;
while (!feof(fid))
n++
tline=strsplit(fgetl(fid),',')
datestring(n)=sprintf('%s',tline{1});
%cname(n)=sprintf('%s',tline{2});
price(n)=str2double(tline{3});
volume(n)=str2num(tline{4});
endwhile
fclose(fid)

Now when I run it, I get the following error due to datestring(n)=sprintf('%s',tline{1});
fname = /tmp/VIXts.csv
ans = 0
tline =

{
  [1,1] = 01/03/2012
  [1,2] = H (Mar 12)
  [1,3] = 26.750000
  [1,4] = 2584
}

error: A(I) = X: X must have the same size as I

how do I capture all the datestrings.

thanks,
Bobby