comp.lang.idl-pvwave archive
Messages from Usenet group comp.lang.idl-pvwave, compiled by Paulo Penteado
Home » Public Forums » archive » Negative Variance?
Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend  		Switch to threaded view of this topic Create a new topic Submit Reply
Negative Variance? [message #65774] Thu, 19 March 2009 15:00
anniebryant@gmail.com is currently offline  anniebryant@gmail.com
Messages: 16
Registered: March 2009
Junior Member
I am using the VARIANCE comand in IDL and am getting negative values.
The description in the HELP menu for IDL doesn't provide much
information, but from what I know, I thought variance was either an
absolute value or a deviation from a squared number, neither of which
could yield a negative value.

I am looking at the variance for 2 different bands in an AVIRIS
image. I use the same .pro, just change the band I am looking at.
The results for Band 1 (lets call it) make sense: all positive
values. For Band 2, I get a lot of negatives.?! How is this
possible.

These are the values for Band 1:

integer mean std dev minimum maximum n_elements
2633.3 2059.3 0.0000 9367.0 (160686) =
160686

These are the values for Band2:

integer mean std dev minimum maximum n_elements
1167.5 18269. -32768. 32767. (160686) =
160686

Report message to a moderator

  Switch to threaded view of this topic Create a new topic Submit Reply
Previous Topic: Make easy and nice your IDL documentation
Next Topic: Re: Make easy and nice your IDL documentation

-=] Back to Top [=-
[ Syndicate this forum (XML) ] [ RSS ] [ PDF ]

Current Time: Wed Oct 08 19:43:42 PDT 2025

Total time taken to generate the page: 0.00443 seconds
.:: Contact :: Home ::.

Powered by: FUDforum 3.0.7.
Copyright ©2001-2013 FUDforum Bulletin Board Software