RES: autocorrelation

[David Mendes]

Guilherme,

 Two new correlation function are available in GrADS version 1.6:

scorr: This function does spatial correlation and returns a single number. It can be used in conjunction with tloop/define to do time series or time/height plots. It's arguments are similar to aave; the areal averages done in scorr are weighted.

scorr (expr1, expr2, lon=..., lon=..., lat=..., lat=...)

tcorr: This function does correlations between two time series. The first argument is an expression that is assumed to give a time series that has a single value per time; the 2nd expression is assumed to give a time seris that is a grid at each time. The first time series is correlated to the time series at each point in the 2nd argument; the result is a 2-D grid of correlation values.

tcorr (expr1, expr2, t = ..., t = ...)

Example:

set x 1 set y 1 set z 1 set t 1 100 define elnino = aave(ts,lon=-160,lon=-80,lat=-20,lat=10) set lon -180 180 set lat -90 90 set z 1 set t 1 d tcorr(elnino, slp, t=1, t=100)

Dr. David Mendes
University of Lisbon,  Phisics Departament
Geophysical Centre,  Meteorology Group
email: dmendes at fc.ul.pt
Tel: (351) 933566291



-----Mensagem original-----
De: GRADSUSR at LIST.CINECA.IT em nome de Guilherme Martins
Enviada: qui 04-01-2007 17:30
Para: GRADSUSR at LIST.CINECA.IT
Assunto:      autocorrelation

hi everybody, i'd like know how i calculate the autocorrelation using grads...
  thanks
  someone can help me?

  my dataset have interval time 06h (00, 06, 12 e 18UTC), 1 up to 123 times

 __________________________________________________
Fale com seus amigos  de graça com o novo Yahoo! Messenger
http://br.messenger.yahoo.com/