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Re: Problem with precision


From: Martijn
Subject: Re: Problem with precision
Date: Thu, 16 Jun 2011 17:15:59 +0200

Hi Fritz,
Try formatted output:
f = fopen("myfile.txt", "w");
fprintf(f, "%.3f\n", mydata);
fclose(f);

The string "%.3f\n" is the formatting string, saying that every number
is to be written als fixed point with 3 decimal, and is to be followed
by a newline.
To write in two columns with a tab as separation or with a fixed column
width use: "%.3f\t%.3f\n" or "%8.3f%12.3f\n".
Beware that to write a file with 2 columns the data matrix needs to have
two rows. So if:
mydata = [x1, y1; x2, y2; ...; xn, yn]
then use
fprintf(f, "%.3f\t%.3f\n", mydata');
Notice the conjugation! This is a quirk that octave has to be compatible
with Matlab.

good luck,

Martijn


On Thu, 2011-06-16 at 16:34 +0200, Fritz Fischer wrote:
> Hello!
> 
> I have a problem with Octave's precision and hope that you can help
> me.
> 
> My function writes data to a file, usually using a normal precision.
> But some
> values are written with a very high precision and in the exponential
> format:
> 
> 44.875
> 40.262
> 35.327
> 30.005
> 20.981
> 6.9638e-28
> 0
> 0
> 
> Can someone tell me how to fix this? I tried format short and format
> long
> but the output is the same at both settings.
> 
> Since the files are used as input for another program that does not
> understand the exponential format I need to change this.
> 
> Kind regards,
> Walter
> 
> 
> 
> 
> 
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