[daip] XMOM2

[Eric Greisen]

On 8/4/19 5:44 AM, Lawrence Rudnick wrote:
> Eric -  I think i've asked you this before, but there seems to be a 
> disconnect between the description of of XMOM2 as the 2nd moment, and 
> its units of degrees, as opposed to degrees^2 ?
> 
> is XMOM2 really = sqrt(2ndmoment-firstmoment^2) ?
> 
> thanks.  lr
> 

That is what is computed.

S1 = Sum (flux * i)
S2 = Sum (flux * i * i)
s1 = s1 / sum (flux)
s2 = s2 / sum (flux)
s2 = sqrt (s2 - s1 * si)

The help file is really short of information about this.

Eric