# [ncl-talk] Probability Calculation

Thu Aug 27 12:07:27 MDT 2015

```Dear NCL,

I have been working on creating a plot with correlation and probability
function. I am able to do it with no lag between two variables, but when I
introduce lag, the probability function is not working, I am not sure why
that is, it will be great if you could guide me on this:-

;This is for correlating JJAS monthly precp with JJAS temperature with lag

;******************************************************
;*******************************************************

;=============================================
;=============================================

;==============================================

JJAS_1871_2012
;Extracting JJAS for 1967 to 2012

JJAS_1967_2012=JJAS_1871_2012(96:141,0)
print(dimsizes(JJAS_1967_2012))

e=transpose(transpose(JJAS_1967_2012))
;print(dimsizes(e))

;=============================================

;For some months around september it is better to
;=============================================
;The dataset goes from 1854-2015
sst=a->sst
; copy meta data and coordinate variables using contributed functions
copy_VarAtts(a,sst)
copy_VarCoords_1(a,sst)
;============================================

;Extracting 1967-2012 for SST
sst_1967_2012=sst(1367:1918,:,:)

copy_VarAtts(sst,sst_1967_2012)
copy_VarCoords_1(a,sst_1967_2012)

;============================================
;Seasonal three month average

sst_djf=month_to_season(sst_1967_2012, "DJF")

;==============================================
;Copying Attributes and Coordinates

copy_VarAtts(sst_1967_2012,sst_djf)
copy_VarCoords_1(sst_1967_2012,sst_djf)
;Calculating correlation

djf_reorder=sst_djf(lat|:,lon|:,time|:)

;Calculating Correlation Coefficient

;Months with Lag
corr_djf=esccr(JJAS_1967_2012,djf_reorder,1)

;========================================
;Probability
x=corr_djf(:,:,1)
print(dimsizes(x))
;==============================
; Now plotting the correlation

;===========================================

; Now plotting the correlation

wks  = gsn_open_wks("pdf","DJF_sst_jjas_cor_prob_sig_lag")
gsn_define_colormap(wks,"BlWhRe")              ; choose colormap

res                      = True                ; make plot mods
res at gsnDraw = False
res at gsnFrame = False
res at cnFillOn             = True                ; turn on color
res at gsnSpreadColors      = True                ; use full colormap
res at lbLabelAutoStride    = True         ; automatic lb label stride

res at cnLinesOn            = False               ; turn off contour lines
res at cnLevelSelectionMode = "ManualLevels" ; manually set cnlev
res at cnMinLevelValF       = -1.                 ; min level
res at cnMaxLevelValF       =  1.                 ; max level
res at cnLevelSpacingF      = .1                  ; contour level spacing

lag                      = 0
res at tiMainString         = "DJF SST with JJAS rainfall"
plotA = gsn_csm_contour_map_ce(wks,corr_djf,res)

; Significance plot on top of correlation plot
;========================= PLOT 2 =========
res2 = True                            ; res2 probability plots

res2 at gsnDraw             = False       ; Do not draw plot
res2 at gsnFrame            = False       ; Do not advance frome
res2 at cnFillOn = True                   ; turn on color/pattern fill
res2 at cnMonoFillPattern = False   ; allow different patterns
res2 at cnMonoFillColor = True       ; only use one color (black)

res2 at cnLevelSelectionMode = "ExplicitLevels" ; set explicit cnlev
res2 at cnLevels   = (/.90/)    ; only have 1 contour level
res2 at cnFillPatterns = (/-1,17/) ; don't fill <0.95, stipple >=0.95

res2 at gsnAddCyclic = True   ; may or may not be needed

res2 at cnInfoLabelOn       = False       ; turn off info label

res2 at cnLinesOn           = False       ; do not draw contour lines
res2 at cnLineLabelsOn      = False    ; do not draw contour labels

res2 at cnFillScaleF        = 0.5         ; add extra density

printMinMax(prob_djf,0)   ; check to make sure values are
; between 0 and 1.

plot2   = gsn_csm_contour(wks,prob_djf, res2)
overlay (plotA, plot2)

draw (plotA)
frame(wks)
;=================================================

Best Regards
Ipshita
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