[rrd-users] q:how are decimal places calculated on Y-axis? (how to influence)?

[Tobias Oetiker]

Hi Pablo,

Today Pablo Sanchez wrote:

> Howdy,
>
> I have a barometric graph which can display results in hPA or inHG.  I
> store the data in hPA and use a CDEF to convert it to inHG when
> requested.
>
> My problem is that for the graph period, the `inHG' value may vary
> only slightly:
>
>      max:  29.97
>      min:  29.88
>
> I've tinkered with `--y-grid' to get better grid steps (before I was
> only getting one line at 30 and the resulting graphed line was very
> flat.  :):
>
>    --y-grid .01:5
>
> and the line graphs very well.  However, the y-axis labels seem to be
> rounded.  Here's an example of what I see versus what I'd like:
>
>     Wanted     Rendered
>     ------     --------
>     30.05         30
>     30.00         30
>     29.95         30
>     29.90         30
>     29.85         30
>     29.80         30
>
> I've tried using the `--alt-y-grid' option but that didn't help.
>
> I'm using a very old version of RRD on this weather-station laptop:
> 1.2.23
>
> Am I missing an obvious `rrdtool graph' switch or is this a bug in
> this very old version of RRD?  :)
>
> Please advise.
>
> Note, I tried compiling the 1.3 version on this openSUSE 10.3 machine
> and it resulted with no data being logged.  Quite strange.  So I went
> back to thee 1.2.23 version - I even disabled nmap ...

the design goal of the yaxis numbering is that there should not be
more than 3 digits displayed this means that for 1-9 you will see
1.1 to 9.9 but from 10 on you will see no post comma digits ...

using --alt-y-grid should help in your case I guess ... but it
could be that it was broken in 1.2.23 ... if you want to stick to
1.2 you may want to try 1.2.30

cheers
tobi


> Cheers,
>

-- 
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