[ncl-talk] ttest values not plotting
Adam Phillips
asphilli at ucar.edu
Wed Jan 17 13:36:03 MST 2018
Hi Sri,
I think the issue is that you are letting NCL create the contour levels
(for plot2), as you are setting res2 at cnLevelSelectionMode =
"ExplicitLevels" but you are not setting res2 at cnLevels.
gsn_contour_shade uses the existing contour levels to modify the plot, it
does not add them itself. I would suggest doing this:
stat_dispersion(probt,True) ; Make sure your data has values less than
or equal to .05 that can be plotted
;
https://www.ncl.ucar.edu/Document/Functions/Contributed/stat_dispersion.shtml
res2 = True ; res2 probability plots
res2 at gsnDraw = False ; Do not draw plot
res2 at gsnFrame = False ; Do not advance frome
res2 at cnLevelSelectionMode = "ExplicitLevels" ; set explicit cnlev
res2 at cnLevels = (/.05/) ; only have 1 contour level
;res2 at cnFillPatterns = (/-1,17/) ; don't fill <0.95, stipple >=0.95
res at cnFillOn = True
res2 at cnInfoLabelOn = False
res2 at cnLinesOn = False ; do not draw contour lines
res2 at cnLineLabelsOn = False ; do not draw contour labels
res2 at cnFillScaleF = 0.6 ; add extra density
plot2 = gsn_csm_contour(wks,probt,res2)
; add cyclic point
opt = True ; set up parameters for pattern fill
opt at gsnShadeFillType = "pattern" ; specify pattern fill
opt at gsnShadeLow = 17 ; stipple pattern
plot2 = gsn_contour_shade(plot2, 0.05, 3., opt) ; stipple all areas <=
0.05 contour
overlay (plot, plot2)
or, more simply, do not even use gsn_contour_shade:
stat_dispersion(probt,True) ; Make sure your data has values less than
or equal to .05 that can be plotted
;
https://www.ncl.ucar.edu/Document/Functions/Contributed/stat_dispersion.shtml
res2 = True ; res2 probability plots
res2 at gsnDraw = False ; Do not draw plot
res2 at gsnFrame = False ; Do not advance frome
res2 at cnLevelSelectionMode = "ExplicitLevels" ; set explicit cnlev
res2 at cnLevels = (/.05/) ; only have 1 contour level
res2 at cnFillPatterns = (/17,-1/) ; don't fill <0.95, stipple >=0.95
res at cnFillOn = True
res2 at cnInfoLabelOn = False
res2 at cnLinesOn = False ; do not draw contour lines
res2 at cnLineLabelsOn = False ; do not draw contour labels
res2 at cnFillScaleF = 0.6 ; add extra density
plot2 = gsn_csm_contour(wks,probt,res2)
; add cyclic point
overlay (plot, plot2)
Hope that helps. If you have any further questions please respond to the
ncl-talk email list.
Adam
On Wed, Jan 17, 2018 at 1:18 PM, Sri Nandini via ncl-talk <ncl-talk at ucar.edu
> wrote:
> Hello
>
> I am trying to plot ttest values overlay onto the T2m differences, but it
> is not being plotted nor shaded region according to 95%confidence limits
> with ttest.
> Below is the script, i would be grateful if someone could let me know of
> my omission or deletion in the resources plotting attributes.
>
> ;Use NCL's named dimensions to reorder in time.
> ;Calculate the temporal means and variances using the dim_avg and
> dim_variance functions.
> ;Specify a critical significance level to test the lag-one
> auto-correlation coefficient and determine the (temporal) number of
> equivalent sample sizes in each grid point using equiv_sample_size.
> ;Specify a critical significance level for the ttest and test if the means
> are different at each grid point.
> ; This file still has to be loaded manually
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/shea_util.ncl"
>
> yrStrt = 0000
> yrLast = 0100
> ; ==============================================================
> ; Open the file: Read only the user specified period
> ; ==============================================================
> f= addfile("T2M_C.nc", "r") ;Model Control
> TIME = f->time
> YYYY = cd_calendar(TIME,-1)/100 ; entire file
> iYYYY = ind(YYYY.ge.yrStrt .and. YYYY.le.yrLast)
> T41 = f->TREFHT(iYYYY,:,:)
> printVarSummary(T41) ; (time, lat,lon)
> T4 = lonFlip(T41)
> printVarSummary(T4) ; (time, lat,lon)
> T4 at _FillValue = -9.96921e+36
> aveX = dim_avg_n_Wrap(T4, 0) ;; average over the 0th dim
> printVarSummary(aveX) ; (lat,lon)
> varX = dim_variance_n_Wrap(T4,0) ; compute variance
> printVarSummary(varX) ; (lat,lon)
> ;===========================================================
> ===================
>
> f2= addfile("T2M_CC.nc", "r") ;Current Caspian
> TIME2 = f2->time
> YYYY2 = cd_calendar(TIME2,-1)/100 ; entire file
> iYYYY2 = ind(YYYY2.ge.yrStrt .and. YYYY2.le.yrLast)
> air22 = f2->TREFHT(iYYYY2,:,:)
> air2 = lonFlip(air22)
> printVarSummary(air2) ; (time, lat,lon)
> air2 at _FillValue = -9.96921e+36
> aveY = dim_avg_n_Wrap(air2,0) ; average over the 0th dim
> printVarSummary(aveY) ; (lat,lon)
> varY = dim_variance_n_Wrap(air2,0) ; compute variance
> printVarSummary(varY) ; (lat,lon)
> ;===========================================================
> =====================
> ;Use "ttest" to compute the probabilities
> ;===========================================================
> ======================
>
> sigr = 0.05 ; critical sig lvl for r
>
> xEqv = new(dimsizes(varY),typeof(varY),varY at _FillValue)
> printVarSummary(xEqv) ; (lat,lon)
> xEqv = equiv_sample_size (T4(lat|:,lon|:,time|:), sigr,0)
> copy_VarMeta(varY,xEqv)
> printVarSummary(xEqv) ; (lat,lon)
>
> yEqv = new(dimsizes(varY),typeof(varY),varY at _FillValue)
> printVarSummary(yEqv) ; (lat,lon)
> yEqv = equiv_sample_size (air2(lat|:,lon|:,time|:), sigr,0)
> copy_VarMeta(varY,yEqv)
> printVarSummary(yEqv) ; (lat,lon)
>
> ;===========================================================
> =======================
> probt = new(dimsizes(varY),typeof(varY),varY at _FillValue)
>
> probt = ttest(aveY,varY,xEqv,aveX,varX,yEqv,True,False) ; values are
> between 0 and 1
>
> ;probt = 100.*(1. -ttest(aveY,varY,xEqv,aveX,varX,yEqv,True,False)) ; all
> areas whose value > 95 are significant
> printVarSummary(probt) ; (lat,lon)
> copy_VarMeta(varY,probt)
> printVarSummary(probt) ; (lat,lon)
> print(probt) ;check to make sure values are between 0
> and 1.
> ;============================================================
> ;calculate the T2M difference
> ;============================================================
> T2diff = new(dimsizes(aveY),typeof(aveY),aveY at _FillValue)
> printVarSummary(T2diff)
> copy_VarMeta(aveY,T2diff)
> printVarSummary(T2diff)
> T2diff=aveY-aveX
> printVarSummary(T2diff) ; (lat,lon)
> ;====================================================================
> ;Here is a section of my code that draws a color fill plot, and then
> ;overlays contours of statistical significance.
> ;====================================================================
> wks = gsn_open_wks("pdf","T2M_ttest")
> gsn_define_colormap(wks,"BlWhRe")
>
> res = True
> res at cnFillOn = True ; turn on color
> res at gsnSpreadColors = True ; use full colormap
>
> res at cnLinesOn = False ; turn off contour lines
> res at cnLevelSelectionMode = "ManualLevels" ; set manual contour levels
> res at cnMinLevelValF = -2. ; set min contour level
> res at cnMaxLevelValF = 2. ; set max contour level
> res at cnLevelSpacingF = 0.2 ; set contour spacing
>
> res at gsnDraw = False ; Do not draw plot
> res at gsnFrame = False ; Do not advance frome
>
> res at tiMainString = "T2M Difference: 50yrs overlay with ttest"
> res at gsnCenterString = "5% stippled"
> res at gsnLeftString = "K"
>
> res at cnRasterModeOn = True ; Raster mode
> shows grid cells
> plot = gsn_csm_contour_map_ce(wks,T2diff,res)
> plot = ZeroNegDashLineContour (plot)
>
> res2 = True ; res2 probability plots
> res2 at gsnDraw = False ; Do not draw plot
> res2 at gsnFrame = False ; Do not advance frome
> res2 at cnLevelSelectionMode = "ExplicitLevels" ; set explicit cnlev
> ;res2 at cnLevels = (/.95/) ; only have 1 contour level
> ;res2 at cnFillPatterns = (/-1,17/) ; don't fill <0.95, stipple >=0.95
> res at cnFillOn = False
>
> res2 at cnInfoLabelOn = False
> res2 at cnLinesOn = False ; do not draw contour lines
> res2 at cnLineLabelsOn = False ; do not draw contour labels
> res2 at cnFillScaleF = 0.6 ; add extra density
>
> plot2 = gsn_csm_contour(wks,probt,res2)
> ; add cyclic point
>
> opt = True ; set up parameters for pattern fill
> opt at gsnShadeFillType = "pattern" ; specify pattern fill
> opt at gsnShadeLow = 17 ; stipple pattern
> plot2 = gsn_contour_shade(plot2, 0.091, 3., opt) ; stipple all areas <
> 0.09 contour
> overlay (plot, plot2)
>
> draw (plot)
> frame(wks)
>
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--
Adam Phillips
Associate Scientist, Climate and Global Dynamics Laboratory, NCAR
www.cgd.ucar.edu/staff/asphilli/ 303-497-1726
<http://www.cgd.ucar.edu/staff/asphilli>
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