RE: [Tcl-nap-users] Missing values

[salah j. <s_...@ya...>]

Hi peter 
  
  The problem was the data type , i am working with U16 so when i use  NDVI the range suppose to be from -1 to 1. what was happinning is that  when i subtract two numbers like thes 250 -256 i get the missing value  which is 64k after that this value is used again to calculate the NDVI
  
  I.E
  
  250 - 254 / 250+254 --------> 65536/504

Pet...@cs... wrote:          RE: [Tcl-nap-users] Missing values          Hi Sala,
            nap ndvi = 0.0/0.0 
             $ndvi
             _
      This sets x to NaN (not a number)  1.0/0.0  generates Inf. The default missing value for float is NaN. 
    You could use
    nap ndvi = isnan(ndvi) ? maxval : ndvi
  
    to fix the problem
    Cheers
    Peter T
    -----Original Message-----
  From: tcl...@li... [mailto:tcl...@li...] On Behalf Of salah jubeh
  Sent: Monday, 13 March 2006 8:32 PM
  To: NAP
  Subject: [Tcl-nap-users] Missing values
    Hi all
     
    While doing some image analysis i  did NDVI "near-red/near+red" , some pixel values of   both images has zero value thats mean (0-0)/(0-0)  afetr thai i  trid to get the max but i get a strange result.
     
    how can i get the max value in that case.
     
      
     
     
    Yahoo! Mail
  Bring photos to life! New PhotoMail makes sharing a breeze. 
  

  

		
---------------------------------
 Yahoo! Mail
 Use Photomail to share photos without annoying attachments.