[ncl-talk] confused about plotting t-values (manually)
Noelia otero
noeli1680 at gmail.com
Fri Oct 21 07:32:41 MDT 2016
Hi Hoffman,
Thanks for your answer, I think I get it, however I would have to set
the cnLevelSelectionMode
for the second plot (res2, in my case), wouldn't I?
I just realised that if I don't specify any LevelSelectionMode (just
leaving it as automatically), it seems to work..
Anyway, many thanks again,
Best
Noelia
2016-10-20 16:26 GMT+02:00 Hoffman Cheung <hoffmancheung at gmail.com>:
> Hi Noelia,
>
> Let me try to answer this question briefly.
>
> If you use gsn_contour_shade, you have to make sure the "contour" you are
> plotting is there, i.e. 0.05 and 1.960 in your case. Otherwise, the program
> may not work "properly". Say, when you want to shade the parts smaller than
> 0.05, but
>
> case 1: if the program only generates contours greater than 0.05, the plot
> will not be shaded;
> case 2: if the program generates contours smaller than 0.05, then only
> part (not all) of the values smaller than 0.05 is shaded.
>
> By default, the contour levels are set automatically, such that the 0.05
> might not be there. To solve the problem, you have to set
> cnLevelSelectionMode, e.g.
> res at cnLevelSelectionMode = "ExplicitLevels"
> res at cnLevels = (/0., 0.05/) ; depending on which contour intervals want
> to draw
> res at cnLinesOn = False ; turn the resource off if you do not want to draw
> the line (similar for the two resources below)
> res at cnLineLabelsOn = False
> res at cnInfoLabelOn = False
>
> Hope my answer helps you solve the problem.
>
> Best,
> Hoffman
>
>
>
>
> 2016-10-20 9:26 GMT+02:00 Noelia otero <noeli1680 at gmail.com>:
>
>> Hi Mary,
>>
>>
>>
>> I sent a couple of questions few days ago (from gmail) , and I was
>> reading about some problems regarding the mail list, so I thought that
>> maybe my mail has not been received …(I can not see it in the mail list).
>> That's why I also added your email addressee (sorry for the
>> inconvenience).
>>
>>
>> I just wanted to re-send my question (see below), in case you can give me
>> a suggestion.
>>
>>
>>
>> Thanks in advance!
>>
>>
>>
>>
>>
>> I'm doing a composite and I'm plotting significant areas (of anomalies).
>> For that, I computed the t-values manually, and then I was trying to add
>> contour for those significant values. However, I'm a bit confused..since if
>> I used gsn_contour_shade for the values greater that the critical value (in
>> my case) it seems not to work well...so, I 'd like to ask if anyone have a
>> suggestion. This is part of my code:
>>
>>
>>
>>
>>
>> ;Average over the period
>>
>> compos_mera = dim_avg(compos_era(lat|:,lon|:,time|:)) ;reordering
>>
>> compos_mera!0 = "lat"
>>
>> compos_mera!1 = "lon"
>>
>> compos_mera&lat = lat
>>
>> compos_mera&lon = lon
>>
>>
>>
>> ;std
>>
>> composStd = dim_stddev_Wrap(compos_era(lat|:, lon|:, time|:)) ;
>>
>> composStd at _FillValue = -999
>>
>> composVar = dim_variance_n (compos_era,0)
>>
>> composVar at _FillValue = -999
>>
>> n = dimsizes(timeE) ;number of observations
>>
>>
>>
>> ;Compute t-student val for significant
>>
>> Scom = composStd/(sqrt(n))
>>
>> Scom at _FillValue=-999
>>
>> mu = 0 ; set the value to see how anomalies are significantly
>> different from zero
>>
>> tval = (compos_mera - mu)/where(Scom.ne.0, Scom, Scom at _FillValue)
>> ;avoid diving by zero
>>
>> abstval= abs(tval)
>>
>> ;see table ttest 0.05 2-tailed
>>
>> cv = 1.960 ;critival value according to the tables
>>
>>
>>
>>
>>
>> ;-------Starting plot------
>>
>>
>>
>> res = True ; plot mods desired
>>
>> res at mpProjection = "LambertConformal"; choose projection
>>
>> res at mpFillOn = False ; turn off map fill
>>
>> res at cnFillOn = True ; turn on color
>>
>> res at cnLinesOn = False ; turn off contour lines
>>
>> res at lbLabelBarOn = True
>>
>> res at gsnDraw = False
>>
>> res at gsnFrame = False
>>
>> res at gsnAddCyclic = False ; regional plot
>>
>> res at gsnMaximize = True ; enlarge plot
>>
>> res at mpMinLatF = 30 ; min lat to mask
>>
>> res at mpMaxLatF = 75 ; max lat to mask
>>
>> res at mpMinLonF = -20 ; min lon to mask
>>
>> res at mpMaxLonF = 40 ; max lon to mask
>>
>> res at gsnMaskLambertConformal = True ; turn on lc masking
>>
>> res at gsnMaskLambertConformalOutlineOn = False ; turns off outline
>>
>>
>>
>> ;----Plot 2plot (significant values )----
>>
>> ; generate shadow plot to overlay
>>
>> res2 = True
>>
>> res2 at gsnAddCyclic = False
>>
>> res2 at gsnDraw = False
>>
>> res2 at gsnFrame = False
>>
>> res2 at cnInfoLabelOn = False
>>
>> res2 at cnLinesOn = False ; do not draw contour lines
>>
>> res2 at cnFillScaleF = 0.9
>>
>>
>>
>> opt = True
>>
>> opt at gsnShadeFillType = "pattern"
>>
>> opt at gsnShadeHigh = 10
>>
>>
>>
>>
>>
>> plot= gsn_csm_contour_map(wks, compos_mera,res)
>>
>> plot2 = gsn_csm_contour(wks,abstval,res2)
>>
>> plot2= gsn_contour_shade(plot2,-999,cv,opt)
>>
>>
>>
>> overlay (plot, plot2)
>>
>>
>>
>>
>>
>> I also tried to computed the p-values and then make the plot, as follows:
>>
>>
>>
>> dim_s = dimsizes(tval) ;lat x lon
>>
>> df = new((/dim_s(0),dim_s(1)/),"integer")
>>
>> df = n-1
>>
>> beta_b = new((/dim_s(0),dim_s(1)/),"float") ; preallocate space
>> for beta_b
>>
>> beta_b = 0.5 ;
>> set entire beta_b array to 0.5, the suggested value of beta_b
>>
>> ; according to betainc documentation
>>
>>
>>
>> prob = betainc( df/(df+tval^2), df/2.0, beta_b)
>>
>> ; Now set up for significant at 0.05
>>
>>
>>
>>
>>
>> opt = True
>>
>> opt at gsnShadeFillType = "pattern"
>>
>> opt at gsnShadeLow = 10
>>
>>
>>
>> plot= gsn_csm_contour_map(wks,compos_mera,res)
>>
>> plot2 = gsn_csm_contour(wks,prob,res2)
>>
>> plot2= gsn_contour_shade(plot2,0.05,-999,opt)
>>
>>
>>
>> Both ways should be OK, am I wrong? What am I missing here, because
>> looking at the values, there are significant values, but I don't know why I
>> can't see it.
>>
>>
>>
>>
>>
>> Also, regarding my other question, if I want to use bootstrap for showing
>> significant anomalies…anyone could give an idea about how to use it? I was
>> wondering if there would be any example about that.
>>
>>
>>
>>
>> Thanks again!
>>
>>
>>
>> Best
>>
>>
>>
>> Noelia.
>>
>>
>>
>> _______________________________________________
>> ncl-talk mailing list
>> ncl-talk at ucar.edu
>> List instructions, subscriber options, unsubscribe:
>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20161021/c6ddbc3c/attachment.html
More information about the ncl-talk
mailing list