[rrd-users] logarithmic scale question

[Tobias Oetiker]

Hi Karl,

this sounds like a sensible aproach ... except that the * thing
will probably not be portable ...

if you create a patch it must be for 1.3.x and the feature should
only be active if units-exponent is set.

cheers
tobi




> Tobias Oetiker wrote:
> > Hi Karl,
> >
> > if you cann make a suggetion as to where you would expect to find
> > this information I will be glad to add it.
>
> Hi Tobi,
>
> I would expect a hint to be near the explanation of --logarithmic
> and especially near --units-exponent
> (e.g. "doesn't work in combination with --logarithmic")
>
> similar to some or the rpn-explanations ( ... doesn't work with VDEF )
>
>
> However, what I really would like is to make it work :-)
>
> I mean, it's no more than a printf "%f" vs printf "%e", isn't it?
>
> Attached is a little example numprint() that would format the numbers
> without exponent as long as they fit into units-length and use exponential
> display beyond that ... wouldn't that be a way to do it?
>
>
> Cheers
>
> - Karl
>
>
> > Today Karl Fischer wrote:
> >
> >> Tobias Oetiker wrote:
> >>> Yesterday Karl Fischer wrote:
> >>>
> >>>> But rrdgraph seems to ignore the --units-exponent=0 directive completely.
> >>>>
> >>>> using Version 1.2.23
> >>>>
> >>>> What am I doing wrong?
> >>> nothing ... log graphs are labled with exponential y axis ticks ...
> >>>
> >>> cheers
> >>> tobi
> >> thanks tobi.
> >> ... might be worth a word in the documentation though ...
> >>
> >> - Karl
>
>
> test.c
>
> #define _GNU_SOURCE
> #include <stdio.h>
> #include <math.h>
>
> int units_length = 8;
>
> void numprint(double num) {
>     int dist;
>     int length = units_length-1;
>     int decimals;
>
>     dist = floor(log10(fabs(num)));
>     decimals = dist > 0 ? 0 : abs(dist);
>
>     if (dist >  length ||
>         dist <= (length * -1) ) {
>         printf ("%.*le", length - 5, num);
>     } else {
>         printf ("%*.*lf", units_length , decimals, num);
>     }
> }
>
> int main() {
>     double number;
>     for (number = pow10(units_length + 1); number > pow10(units_length * -1);  number /= 10 ) {
>         printf ("%.0le:  ", number);
>         numprint(number);
>         printf ("\n");
>     }
> }
>
>
>
>
> will output something like:
>
> 1e+09:  1.00e+09
> 1e+08:  1.00e+08
> 1e+07:  10000000
> 1e+06:   1000000
> 1e+05:    100000
> 1e+04:     10000
> 1e+03:      1000
> 1e+02:       100
> 1e+01:        10
> 1e+00:         1
> 1e-01:       0.1
> 1e-02:      0.01
> 1e-03:     0.001
> 1e-04:    0.0001
> 1e-05:   0.00001
> 1e-06:  0.000001
> 1e-07:  1.00e-07
> 1e-08:  1.00e-08
>
>

-- 
Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten, Switzerland
http://it.oetiker.ch tobi at oetiker.ch ++41 62 775 9902 / sb: -9900