[ncl-talk] stat_despersion

[Buzan, Jonathan]

NCL counts from 0 to n-1, not from 1 to n. So your loop vars need to account for that.

Cheers,
-Jonathan



On Jun 30, 2021, at 1:10 PM, ali mughal via ncl-talk <ncl-talk at mailman.ucar.edu<mailto:ncl-talk at mailman.ucar.edu>> wrote:

Dear community
Thank you very much for your helpful comments.
As an initial test, I was trying to obtain statistics at all grid points before plotting them. I used the following code
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
a=addfile("wrfout","r")
ta_mean_BEM=a->TA_MEAN
ta=ta_mean_BEM(24:719,0,:,:)
rf=ta-273.16
nlat1=rf(0,:,0)
printVarSummary(nlat)
mlon1=rf(0,0,:)
printVarSummary(mlon)
printVarSummary(rf)
opt=False


     nlStrt=0
     nlLast=129
     mlStrt=0
     mlLast=210
     nlat=dimsizes(nlat1)
     mlon=dimsizes(mlon1)

    grid_stats = new ((/nlat(0),mlon(0)/), typeof(rf), getFillValue(rf))
    printVarSummary(grid_stats)
    do nl=0,nlLast
      do ml=0,mlLast

         grid_stats(nl-nlStrt,ml-mlStrt) = stat_dispersion( rf(:,nl,ml), opt)

      end do
   end do

   copy_VarCoords(rf(:,nlStrt:nlLast,mlStrt:mlLast), grid_stats)
   grid_stats at long_name = "stat_dispersion at individual grid points"
   printVarSummary(grid_stats)

But I obtain the following output from my print statements and the errors

Variable: rf
Type: float
Total Size: 75418560 bytes
            18854640 values
Number of Dimensions: 3
Dimensions and sizes:   [696] x [129] x [210]
Coordinates:

Variable: grid_stats
Type: float
Total Size: 108360 bytes
            27090 values
Number of Dimensions: 2
Dimensions and sizes:   [129] x [210]
Coordinates:
fatal:VarVarWrite: Number of dimensions on left hand side does not match right hand side
fatal:["Execute.c":8578]:Execute: Error occurred at or near line 46 in file var_Test.ncl

fatal:Subscript out of range, error in subscript #1
fatal:An error occurred reading rf
fatal:["Execute.c":8578]:Execute: Error occurred at or near line 51 in file var_Test.ncl


Variable: grid_stats
Type: float
Total Size: 108360 bytes
            27090 values
Number of Dimensions: 2
Dimensions and sizes:   [129] x [210]
Coordinates:
Number Of Attributes: 1
  long_name :   stat_dispersion at individual grid points






On Wed, Jun 30, 2021 at 12:01 AM Dave Allured - NOAA Affiliate <dave.allured at noaa.gov<mailto:dave.allured at noaa.gov>> wrote:
Ali, you do not need to make new code to find the 10th and 90th percentile values.  Just use stat_dispersion directly, and take only the output values that you need.  The function is designed to be used in this way.  There is no significant performance impact from ignoring all the other result values.

You can easily make a spatial map of 10th or 90th percentile values.  Just call stat_dispersion inside a double loop over X and Y dimensions.


On Tue, Jun 29, 2021 at 9:23 AM Buzan, Jonathan via ncl-talk <ncl-talk at mailman.ucar.edu<mailto:ncl-talk at mailman.ucar.edu>> wrote:
Hello,

I’ve used that function a bunch. If you only want 10th and 90th percentile, you’ll want to use:

qsort
Which will sort your data within a single grid cell from lowest to highest.

And then grab the specific lines of code for 10th and 90th percentiles from the stat_dispersion function in:
$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl

If you look at the function, you’ll see that it uses qsort, then goes step by step through calculating all the different applications.

Cheers,
-Jonathan

On Jun 29, 2021, at 5:14 PM, ali mughal via ncl-talk <ncl-talk at mailman.ucar.edu<mailto:ncl-talk at mailman.ucar.edu>> wrote:

Dear NCL community

In the following ncl function

http://www.ncl.ucar.edu/Document/Functions/Contributed/stat_dispersion.shtml

Is it possible to use 10th and 90th percentile values only ?

Also can these values be used to develop a spatial map?

For example if I want to find the 10th and  90th percentile of air temperature within the urban grid cells only.

Can anyone share an example script or point me to any web resource will be appreciated.

Thanks in advance
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