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Re: Problem with precision

From: HomeRun4711
Subject: Re: Problem with precision
Date: Thu, 16 Jun 2011 20:02:36 +0200
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv: Gecko/20110424 Lightning/1.0b2 Thunderbird/3.1.10

Hi Martijn,

thanks for your reply. This makes sense.
I will format the output from now on.

Kind regards,

Am 16.06.2011 19:51, schrieb Martijn:
Hi Walter,
There was no problem. You just did not specify the formatting, so a sane
default was chosen. Rounding small number to 0, as is done when saving
in 3 decimal fixed point notation, is in many cases undesirable.
If you want something different, well, specify the formatting.


On Thu, 2011-06-16 at 18:55 +0200, Fritz Fischer wrote:

Thanks for you quick responses. Ok, I will rewrite my function.
So far I was using

fprintf(fd,['time', num2str(timeStep),'\n']);

Just to learn something -  can someone tell me what exactly
was causing the problem?

Kind regards,

2011/6/16 Martijn<address@hidden>
         Hi Fritz,
         Try formatted output:
         f = fopen("myfile.txt", "w");
         fprintf(f, "%.3f\n", mydata);

         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
         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
         with Matlab.

         good luck,


         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
         >  But some
         >  values are written with a very high precision and in the
         >  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

         >  _______________________________________________
         >  Help-octave mailing list
         >  address@hidden

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