gnuplot-beta

Format "%5f" vs. "%5g"

[Theo H. <th...@ph...>]

Hi all. Why does `set format y "%5f"` not work like `set format y 
"%5g"`? I'm dealing with numbers between 0 and 5, so I would expect both 
to produce tic labels with right justified floating point numbers in a 
field of five characters, with no trailing zeros. %5g does, but %5f 
doesn't: it produces tic labels with six decimal places and trailing zeros.

I've tried 4.2.3 and the latest CVS on Cygwin, and 4.3.0 (dated February 
2008) on Linux.

Minimal example:

reset
plot x
set format y "%5g"
replot
set format y "%5f"
replot

According to my interpretation of the documentation, the last two plots 
should be identical.

THeo

Re: Format "%5f" vs. "%5g"

[Ethan A M. <merritt@u.washington.edu>]

On Tuesday 29 July 2008, Theo Hopman wrote:
> Hi all. Why does `set format y "%5f"` not work like `set format y 
> "%5g"`? I'm dealing with numbers between 0 and 5, so I would expect both 
> to produce tic labels with right justified floating point numbers in a 
> field of five characters, with no trailing zeros. %5g does, but %5f 
> doesn't: it produces tic labels with six decimal places and trailing zeros.

That is the C standard.
From "man sprintf"

       f,F    The double argument is rounded and converted to decimal notation in the style
              [-]ddd.ddd,  where  the number of digits after the decimal-point character is
              equal to the precision specification.  If the precision  is  missing,  it  is
              taken  as  6; if the precision is explicitly zero, no decimal-point character
              appears.  If a decimal point appears, at least one digit appears before it.





> I've tried 4.2.3 and the latest CVS on Cygwin, and 4.3.0 (dated February 
> 2008) on Linux.
> 
> Minimal example:
> 
> reset
> plot x
> set format y "%5g"
> replot
> set format y "%5f"
> replot
> 
> According to my interpretation of the documentation, the last two plots 
> should be identical.
> 
> THeo
> 
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-- 
Ethan A Merritt
Biomolecular Structure Center
University of Washington, Seattle 98195-7742

Re: Format "%5f" vs. "%5g"

[Allin C. <cot...@wf...>]

On Tue, 29 Jul 2008, Theo Hopman wrote:

> Hi all. Why does `set format y "%5f"` not work like `set format 
> y "%5g"`? I'm dealing with numbers between 0 and 5...

That's the way things are in C (man 3 printf).

waverley:~/cfiles/misc$ cat fg.c
#include <stdio.h>

int main (void)
{
    int i;

    for (i=0; i<3; i++) {
        printf("5f:   %5f\n", (double) i);
        printf("5g:   %5g\n", (double) i);
        printf("5.0f: %5.0f\n", (double) i);
    }

    return 0;
}
waverley:~/cfiles/misc$ gcc -Wall fg.c
waverley:~/cfiles/misc$ ./a.out 
5f:   0.000000
5g:       0
5.0f:     0
5f:   1.000000
5g:       1
5.0f:     1
5f:   2.000000
5g:       2
5.0f:     2

Allin Cottrell

Re: Format "%5f" vs. "%5g"

[Hans-Bernhard B. <HBB...@t-...>]

Theo Hopman wrote:
> Hi all. Why does `set format y "%5f"` not work like `set format y 
> "%5g"`? 

Because it doesn't.  Nor is it supposed to.

It would be rather silly to have commands be different if they did the 
exact same thing, wouldn't it?

> I'm dealing with numbers between 0 and 5, so I would expect both 
> to produce tic labels with right justified floating point numbers in a 
> field of five characters, with no trailing zeros. %5g does, but %5f 
> doesn't: it produces tic labels with six decimal places and trailing zeros.

I'm afraid your expectation is based on reading the wrong documentation. 
  First of all, the '5' in %5f doesn't mean that the output should be 
exactly 5 characters wide.  It says that it shall be *at least* 5.  And 
it did that.

Second, if you wanted the output to fit into exactly 5 chars, you would 
have to fix the precision, too.  As is, you left that choice to the C 
compiler that made your version of gnuplot.  It picked 6, but you want 2:

	set format '% 5.2f'  # keep that ' ' after the '%'!