Re: [hobbit] More Temperature Questions :-)

[Charles Jones <jonescr (at) cisco.com>]

Thanks Henrik, as usual your advice worked like a charm.  I also changed 
the GPRINT statements to use tempf so the legend would be correct.  
Final version:


[temperature]
       FNPATTERN temperature.(.*).rrd
       TITLE Temperature
       YAXIS Fahrenheit
       DEF:p (at) RRDIDX@= (at) RRDFN@:temperature:AVERAGE
       CDEF:tempf (at) RRDIDX@=9,5,/,p (at) RRDIDX@,*,32,+
       LINE2:tempf (at) RRDIDX@# (at) COLOR@:@RRDPARAM@
       GPRINT:tempf (at) RRDIDX@:LAST: \: %5.1lf (cur)
       GPRINT:tempf (at) RRDIDX@:MAX: \: %5.1lf (max)
       GPRINT:tempf (at) RRDIDX@:MIN: \: %5.1lf (min)
       GPRINT:tempf (at) RRDIDX@:AVERAGE: \: %5.1lf (avg)\n

Thanks again!
-Charles

Henrik Stoerner wrote:

> On Tue, Feb 15, 2005 at 11:49:55AM -0700, Charles Jones wrote:
>  
>
> > 1. How can I graph Farenheit instead of Celcius?
> >    
>
> The easiest way of doing that is to change the hobbitgraph.cfg
> definition for the graph!
>
> In the [temperature] section, there's this line that picks out the
> "temperature" setting from the RRD file:
>
>    DEF:p (at) RRDIDX@= (at) RRDFN@:temperature:AVERAGE
>
> This is an RRDtool "DEF" (definition) that defines a variable
> "p (at) RRDIDX@" (the "@RRDIDX@" is handled by hobbitgraph, and is needed
> because there are multiple graphs. So essentially you get p0, p1, p2
> etc - one for each temperature*rrd file). 
>
> There's also something called a "CDEF" - a Computed DEFinition.
> Meaning you can do math on the data you have in the RRD. So to compute
> Fahrenheit, you do the usual F = (9/5)*C + 32 - using Reverse Polish
> Notation (RPN) which is what CDEF's understand:
>
>   CDEF:tempf (at) RRDIDX@=9,5,/,p (at) RRDIDX@,*,32,+
>
> Now you have two values: p (at) RRDIDX which is the original Celsius
> temperature, and tempf (at) RRDIDX@ which is the Fahrenheit equivalent.
> So to get the graph for the Fahrenheit one, change the LINE2 graph
> definition to use the Fahrenheit value:
>
>   LINE2:tempf (at) RRDIDX@# (at) COLOR@:@RRDPARAM@
>
>
> Finally you just change the Y-axis label, and end up with this
> definition:
>
> [temperature]
>        FNPATTERN temperature.(.*).rrd
>        TITLE Temperature
>        YAXIS Fahrenheit
>        DEF:p (at) RRDIDX@= (at) RRDFN@:temperature:AVERAGE
>        CDEF:tempf (at) RRDIDX@=9,5,/,p (at) RRDIDX@,*,32,+
>        LINE2:tempf (at) RRDIDX@# (at) COLOR@:@RRDPARAM@
>        GPRINT:p (at) RRDIDX@:LAST: \: %5.1lf (cur)
>        GPRINT:p (at) RRDIDX@:MAX: \: %5.1lf (max)
>        GPRINT:p (at) RRDIDX@:MIN: \: %5.1lf (min)
>        GPRINT:p (at) RRDIDX@:AVERAGE: \: %5.1lf (avg)\n
>
>
> Untested, but you get the idea ... the RRDtool website has some more
> examples and tutorials on CDEF's.
>
>
> Regards,
> Henrik
>
> To unsubscribe from the hobbit list, send an e-mail to
> hobbit-unsubscribe (at) hswn.dk
>