On Fri, 2009-07-10 at 09:48 -0700, Ansley Manke wrote:
> Hi Xia,
> The script ef_eof_demo.jnl is contained in the fer_environment.tar
> file from the Ferret downloads pages, so if you have installed Ferret
> it should be available in your scripts directory. I will copy it
> below for you as well. We also have an html version of this demo,
> which can be found under the "tutorials" link on the Ferret
> documentation page.
>
>
http://ferret.pmel.noaa.gov/FERRET_17sep07/Demos/ef_eof_demo/ef_eof_demo.html
>
>
>
> \SET MODE VERIFY
> ! ef_eof_demo.jnl ( acm 9/2000)
>
> ! Description: Demonstration of computing EOFs using the
> ! External Functions EOF_SPACE, EOF_TFUNC, EOF_STAT
>
> ! The functions implements Chelton's '82 method for finding EOFs of
> gappy
> ! time series. All the functions perform the same computation but
> return
> ! different portions of the results.
>
> ! * EOF_SPACE returns EOF eigenvectors: spatial EOF in x and y with
> the
> ! same units as the incoming data
> ! * EOF_TFUNC returns EOF time amplitude functions; dimensionless
> ! * EOF_STAT returns statistics on the EOF computation: number of
> EOFs
> ! scaled and returned; Percent variance explained by each EOF; and
> the
> ! eigenvalues.
> !
> ! For all functions the arguments are as follows:
> !
> ! * 1st argument: Input data field, a function of x, y, and time;
> may be a
> ! function of z
> ! * 2nd argument: The minimum percent variance explained by the
> EOF's that
> ! are computed and scaled, e.g. to return EOFs that explain at
> least 2%
> ! variance, use 2.0
> ! * 3nd argument: The fraction of each time series that must be
> present to
> ! include it in the calculations, e.g. to use all time series that
> have
> ! at least half the data present, use 0.5
> !
> !
> ! EOF functions Example 1: define a function of x,y,time using trig
> ! functions. Decompose into spatial and time EOF's and display
> statistics.
> !
> PAUSE
> LET time = t[t=1-jan-1990:10-jan-1990:24] ! 24 hour resolution time
> axis
>
> DEFINE AXIS/x=0:10:0.5 x10
> DEFINE AXIS/y=0:10:0.5 y10
> DEFINE GRID/x=x10/y=y10/t=time g10x10
> SET GRID g10x10
>
> LET fcn1 = 15.* sin(omega1*t)*cos(r)/(r+1)
> LET fcn2 = 20.* sin(omega2*t)*(sin(s)-.2*sin(q))/(s+1)
>
> LET r = ((6.*(xpts-x0)^2 + 7.*(ypts-y0)^2)^0.5)
> LET s = (((xpts-x1)^2 + 2*(ypts-y1)^2)^0.5)
> LET q = ((3*(xpts-x0)^2 + (ypts-y1)^2)^0.5)
>
> LET x0 = 2
> LET y0 = 4
> LET x1 = 5
> LET y1 = 7
>
> LET omega1 = 1/10*2*3.14159
> LET omega2 = 2 * omega1
>
> LET sample_function = fcn1 + fcn2
> LET xpts = x
> LET ypts = y
>
> ! Compute the statistics on the EOF solution. EOF_STAT returns:
> ! for J=1 the number of EOFs returned
> ! for J=2 the percent variance explained by each EOF
> ! for J=3 the eigenvalue for each EOF
>
> LET estat = eof_stat(sample_function, 0.1)
>
> LIST/I=1/J=1 estat
>
> LIST/I=1:4/J=2 estat
>
> LIST/I=1:4/J=3 estat
>
>
> ! Plot the original function (averaged over time) and its spatial
> ! decomposition by EOF_SPACE
>
> PAUSE
>
> DEFINE VIEW/xlim=0.,.33/ylim=.6,1./text=0.2 vul
> DEFINE VIEW/xlim=.33,.66/ylim=.6,1./text=0.2 vuc
> DEFINE VIEW/xlim=.66,1./ylim=.6,1./text=0.2 vur
>
> DEFINE VIEW/xlim=0.,.33/ylim=.1,.5/text=0.2 vll
> DEFINE VIEW/xlim=.33,.66/ylim=.1,.5/text=0.2 vlc
> DEFINE VIEW/xlim=.66,1./ylim=.1,.5/text=0.2 vlr
>
> SET VIEW vul; CONTOUR/TITLE="FCN1" fcn1[l=1:10@ave]
> SET VIEW vuc; CONTOUR/TITLE="FCN2" fcn2[l=1:10@ave]
> SET VIEW vur; CONTOUR/TITLE="FCN1 + FCN2" sample_function[l=1:10@ave]
>
>
> LET exy = eof_space(sample_function, 0.1)
>
> SET VIEW vll; CONTOUR/L=1/TITLE="EOF 1" exy
> SET VIEW vlc; CONTOUR/L=2/TITLE="EOF 2" exy
>
> PAUSE
> CANCEL VIEW
>
> ! Now plot the time amplitude functions.
>
> LET etim = eof_tfunc(sample_function, 0.1)
>
> SET VIEW ul
> PLOT/I=1/TITLE=taf1 etim
>
> SET VIEW ur
> PLOT/I=2/TITLE=taf2 etim
>
> ! should be all bad flags...
> SET VIEW ll
> PLOT/I=3/TITLE=taf3 etim
>
> PAUSE
> CANCEL DATA/ALL
> CANCEL VARIABLE/ALL
> CANCEL REGION
> CANCEL VIEW
>
> ! A second example, using the COADS climatology data.
> !
>
> USE coads_climatology
> SET REGION/X=67w:1w/Y=11S:11N
>
> ! Compute and save the spatial EOF functions. These have the same
> units
> ! as the data.
>
> LET eof_xyfcn = eof_space(sst, 0.5)
> SAVE/CLOBBER/FILE=sst_clim_eof_space.cdf eof_xyfcn
>
>
> CANCEL DATA/ALL
> CANCEL VARIABLE/ALL
> CANCEL REGION
>
> USE sst_clim_eof_space.cdf
> SET VIEW ul; fill/l=1/TITLE="eof 1" eof_xyfcn; go land
> SET VIEW ur; fill/l=2/TITLE="eof 2" eof_xyfcn; go land
> SET VIEW ll; fill/l=3/TITLE="eof 3" eof_xyfcn; go land
>
> PAUSE
> CANCEL DATA/ALL
> CANCEL VARIABLE/ALL
> CANCEL REGION
>
> ! Compute the statistics on the EOFs: number of EOFs scaled
> ! and returned; Percent variance explained by each EOF; and the
> ! eigenvalues.
>
>
> USE coads_climatology
> SET REGION/X=67w:1w/Y=11S:11N
> LET eofstat = eof_stat(sst[X=67w:1w,Y=11S:11N], 0.5)
>
> LET nout = eofstat[i=1,j=1]
> LET pcts = eofstat[i=1:`nout`,j=2]
>
> LET eigenv = eofstat[i=1:`nout`,j=3]
>
> LIST nout
> LIST/I=1:6 pcts
> LIST/I=1:6 eigenv
>
> PAUSE
>
> ! Compute and save time amplitude functions: Note they are
> dimensionless.
>
> USE coads_climatology
> LET eoftime = eof_tfunc(sst[X=67w:1w,Y=11S:11N], 0.5)
>
> SAVE/CLOBBER/FILE=sst_clim_eof_tfunc.cdf eoftime[i=1:`nout`]
>
> CANCEL VIEW
> CANCEL VARIABLE/ALL
> USE sst_clim_eof_tfunc.cdf
>
> SET VIEW ul
> PLOT/I=1/TITLE="time function 1"/VLIMITS=-2:2:0.5 eoftime
> SET VIEW ur
> PLOT/I=2/TITLE="time function 2"/VLIMITS=-2:2:0.5 eoftime
> SET VIEW ll
> PLOT/I=3/TITLE="time function 3"/VLIMITS=-2:2:0.5 eoftime
>
> \SET MODE/LAST VERIFY
>
>
> Changshui Xia wrote:
> > Dear all,
> > I have a model monthly mean SSHA from 1980-2007,How to use the
> > Ferret EOF function to find the first 3 mode? The file
> > ef_eof_demo.jnl can not be obtained.
> >
> > Thank you.
> >
> > Xia
> >