# how to draw the spectrum result?

From: Xuguang Sun <sunxg007_at_nyahnyahspammersnyahnyah>
Date: Thu, 3 Sep 2009 08:18:53 -0700 (PDT)

Dear everyone,

I finished calculating the spectrum of a time series, and wanted to draw the spectrum by NCL. Because the size of sample is very large, for example, 1000-yr nino3 index from a coupled model, and at the same time, the spectra usually concentrated to a narrow area, like 2yr to 50yr, therefore, it's better to use a log coordinate in the x-axis, and in order to illustrate the result well, I want the unit of x-Axis changing from frequency to period. The following code is part of the whole script to do the above mentioned work, however, it doesn't work, I'd like your suggestions. Thanks in advance.

ts = nino3
iopt = 0 ; remove series mean
jave = 9 ; Average 3 periodogram estimates using modified Daniel
pct = 0.1 ; taper 10% of the data

sdof = specx_anal(ts,iopt,jave,pct)
splt = specx_ci(sdof,0.05,0.95)

print(sdof)
; print(sdof_at_frq)

wks = gsn_open_wks("ps","nino3-spectrum-month")
res = True

res_at_vpXF = 0.2
res_at_vpYF = 0.8
res_at_vpWidthF = 0.6
res_at_vpHeightF = 0.4

res_at_tiYAxisString = "Power" ; yaxis
; res_at_tiXAxisString = "Frequency(cycles/month)" ; xaxis
; res_at_tiXAxisString = "Frequency(cycles/year)" ; xaxis
res_at_tiXAxisString = "Period(year)" ; xaxis
res_at_tiMainString = "Spectrum of monthly nino3 index"
res_at_xyLineThicknesses = (/2.,1.5,1.,1./) ; Define line thicknesses
res_at_xyDashPatterns = (/0,0,1,1/)
res_at_xyLineColors = (/"foreground","red","blue","green"/)

res_at_tmXBMode = "Explicit"
res_at_tmXBStyle = "Log"
res_at_tmXBValues = sdof_at_frq(9:300)
xvalue = 1./(sdof_at_frq(9:300)*12)
res_at_tmXBLabels = flt2string(xvalue)
res_at_tmXBLabelStride = 50

print(res_at_tmXBLabels)

res_at_tmXBTickSpacingF = 1
plot = gsn_csm_xy(wks,sdof_at_frq(9:300),splt(:,9:300),res)

Xuguang

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Received on Thu Sep 03 2009 - 09:18:53 MDT

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