[rrd-users] Practical uses for LSLCORREL?

[Diego M. Vadell]

On Wednesday 30 January 2008 16:14:07 A Darren Dunham wrote:
> On Wed, Jan 30, 2008 at 01:29:02PM -0200, Diego M. Vadell wrote:
> > "LSLCORREL is the Correlation Coefficient (also know as Pearson's Product
> > Moment Correlation Coefficient). It will range from 0 to +/-1 and
> > represents the quality of fit for the approximation."
> >
> > As far as I understand, rrdtool calculates the Least Square Line to
> > approximate the value, and LSLCORREL is how good the approximation
> > is. Like a measure of the confidence in the LSL approximation.
>
> Correct.  So LSLCORREL is one of the values that comes out of the
> calculation of a linear approximation of the data.
>
> > Three questions then:
> > * Am I right? Have I missed something?
>
> Not sure... :-)
>
> > * What is a practical use of LSLCORREL? In fact, why would I want to
> > approximate the data?
>
> If you have data that is not exactly linear, then creating a "best fit"
> line will be only an approximation.  But it is often a useful one.  The
> correlation figure will give a relative measure of how good the fit is.
>
> > * Is there a way to do what I want (find the correlation - e.g. the
> > person's PMCC - of two datasources)?
>
> Not within RRD that I can see.  The LSL stuff appears to be only for
> generating a linear approximation of a single datasource.

Thank you very much Darren.

 -- Diego.