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linguist/samples/NCL/PrnOscPat_driver.ncl
2015-07-09 07:17:01 -07:00

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undef("PrnOscPat_driver")
function PrnOscPat_driver(eof[*][*][*]:numeric, eof_ts[*][*]:numeric, kPOP[1]:integer)
; =================================================================
; compute Principal Oscillation Patterns (POPs)
; =================================================================
local dim_ts, dim_eof, neof, ntim, nlat, mlon, dnam_ts, dnam_eof, neof, j \
, cov0, cov1, cov0_inverse, A, z, Z, pr, pi, zr, zi, mean, stdev \
, evlr, eigi, eigr
begin
dim_ts = dimsizes(eof_ts) ; (neof,ntim)
dim_eof = dimsizes(eof) ; (neof,nlat,mlon)
ntim = dim_ts(1)
neof = dim_eof(0)
nlat = dim_eof(1)
mlon = dim_eof(2)
dnam_ts = getvardims(eof_ts) ; dimension names
dnam_eof= getvardims(eof) ; used at end for meta data
; =================================================================
; lag-0 and lag-1 matrices
; =================================================================
if (get_ncl_version().eq."6.1.2") then ; bug in 6.1.2
cov0 = covcorm(eof_ts,(/1,0/)) ; lag-0 covariance matrix
else
cov0 = covcorm(eof_ts,(/0,1/)) ; lag-0 covariance matrix (n x n)
end if
; either
cov1 = covcorm_xy(eof_ts, eof_ts, (/0,1,0/)) ; lag-1
;cov1 = covcorm_xy(eof_ts(:,0:ntim-2) \ ; alternative, brute force
; ,eof_ts(:,1:ntim-1), (/0,0,0/))
;printVarSummary(cov1)
; =================================================================
; matrix A contains information for evolution of the POP system.
; POPs are eigenvectors of A.
; =================================================================
cov0_inverse = inverse_matrix(cov0)
A = cov1#inverse_matrix(cov0) ; [*][*] => neof x neof
; =================================================================
; NCL 6.1.1 of dgeevx: evlr(2,2,N,N) ; (left(0)/right(1), real(0)/imag(1),:,:)
; Eigenvalues are returned as attributes: eigi = evlr@eigi ; eigr = evlr@eigr
; =================================================================
evlr = dgeevx_lapack(A, "B", "V", "V", "B", False)
; =================================================================
; POP time series from eigenvalues and right eigenvectors
; =================================================================
;PR = (/ evlr(1,0,:,:) /) ; right ev (1), real part (0)
;PI = (/ evlr(1,1,:,:) /) ; right ev (1), imag part (1)
; kPOP is what we want; use righteigenvector
pr = (/ evlr(1,0,kPOP-1,:) /) ; right ev (1), real part (0), row 'kPOP-1'
pi = (/ evlr(1,1,kPOP-1,:) /) ; right ev (1), imag part (1), row 'kPOP-1'
z = inverse_matrix( (/ (/sum(pr*pr), sum(pr*pi)/) \
, (/sum(pr*pi), sum(pi*pi)/) /))#(/pr,pi/)#eof_ts
; complex conjugate
z = (/z(0,:), -z(1,:)/) ; real & imag series
z = dim_rmvmean_n(z,1)
mean = dim_avg_n(z,1) ; calculate mean
stdev= dim_stddev_n(z,1) ; calculate stdev
z = dim_standardize_n(z,1,1) ; standardize time series
z!0 = "nPOP" ; add meta data
z!1 = dnam_ts(1)
z&nPOP = (/0,1/)
z&$dnam_ts(1)$ = eof_ts&$dnam_ts(1)$
z@stdev = stdev
z@mean = mean
z@long_name = "POP timeseries"
;printVarSummary(z)
; =================================================================
; POP spatial patterns
; =================================================================
zr = pr(0)*eof(0,:,:) ; construct POP spatial domain
zi = pi(0)*eof(0,:,:)
do j=1,neof-1
zr = zr + pr(j)*eof(j,:,:)
zi = zi + pi(j)*eof(j,:,:)
end do
Z = (/zr*stdev(0), -zi*stdev(1)/) ; scale patterns by time series stdev
Z!0 = "nPOP" ; add meta data
Z!1 = dnam_eof(1)
Z!2 = dnam_eof(2)
Z&nPOP = (/0,1/)
Z&$dnam_eof(1)$ = eof&$dnam_eof(1)$
Z&$dnam_eof(2)$ = eof&$dnam_eof(2)$
Z@long_name = "POP pattern"
;printVarSummary(Z)
; =================================================================
; return POP time series and POP spatial patterns as a
; variable of type 'list' which contains 2 variables
; =================================================================
return( [/z, Z/] ) ; this is type "list"
end