[rrd-users] Practical uses for LSLCORREL?

[Diego M. Vadell]

Hi,
    I was thinking about finding the correlation between two different 
datasources, and after a little browsing I got back to the rrrdtool home 
page, where it says:

"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.

More browsing led me to the wikipedia:

"In statistics, the Pearson product-moment correlation coefficient (sometimes 
referred to as the MCV or PMCC) (r) is a common measure of the correlation 
between two variables X and Y. "

So everything has sense, except that its not what I was looking for :)

Three questions then:
* Am I right? Have I missed something?
* What is a practical use of LSLCORREL? In fact, why would I want to 
approximate the data?
* Is there a way to do what I want (find the correlation - e.g. the person's 
PMCC - of two datasources)?

Thanks a lot in advance, 

 -- Diego.