[rrd-users] Re: Quick RPN question... (Square root in RPN?)

[Tobias Oetiker]

Today Simon Mullis wrote:

> Hello all,
>
> Am I right in thinking there is no easy way to do a square root in RPN?
>
> I want to calculate a Standard Deviation of a set of values. Anyone done
> this already?
>
> I want to use RPN because I'd like to superimpose the value of the Std Dev
> on the graph of the normal values.
>
> Or should I just use Perl and RRDs::fetch ?
> Thanks

SM,

look at the code for rrd_graph.c adding new functions to RPN is
pretty straight forward ... compare with the SIN function for
example

tobi
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