[hobbit] More Temperature Questions :-)

[Charles Jones]

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@=@RRDFN@:temperature:AVERAGE
        CDEF:tempf at RRDIDX@=9,5,/,p at RRDIDX@,*,32,+
        LINE2:tempf at RRDIDX@#@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@=@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@#@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@=@RRDFN@:temperature:AVERAGE
>        CDEF:tempf at RRDIDX@=9,5,/,p at RRDIDX@,*,32,+
>        LINE2:tempf at RRDIDX@#@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
>
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>hobbit-unsubscribe at hswn.dk
>  
>

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