[ncl-talk] mean value of all displayed grid points / pixel in a map

Wed Sep 3 09:31:16 MDT 2014

Hi Frank,

how are you deciding which area to plot? You must have something in your
code that limits the area shown in the figure. Why don't you just use
coordinate indexing to extract the region of interest from your data and
set everything else to _FillValue. That way you can compute the area
average and only the points that are not missing will be used for the
average. Is that what you were looking for?

Maria

On Wed, Sep 3, 2014 at 12:07 AM, Kreienkamp Frank <Frank.Kreienkamp at dwd.de>
wrote:

>  Hello Dennis,
>
>
>
> if i read the webpage correctly the suggested functions are not what i am
> looking for.
>
>
>
> Yes, I am looking for an areal average.
>
>
>
> No, it is not for an rectangular grid.
>
>
>
> I have an rectangular grid as the ‘base’. Using this grid and a polar
> stereographic projection I am drawing a map. This map is showing  only a
> part of the hole ‘base’ grid. I am looking for an average of this
> shown/drawn part.
>
>
>
> Writing the same from a different view. I am looking for a function what
> calculates the average values of the presented map. See the example in my
> previous e-mail.
>
>
>
> As far a I understand the description correctly this in not what the
> function wgt_areaave_wrap provides.
>
>
>
> Thanks in advance
>
> Frank
>
>
>
> *Von:* Dennis Shea [mailto:shea at ucar.edu]
> *Gesendet:* Montag, 1. September 2014 16:13
>
> *An:* Kreienkamp Frank
> *Cc:* ncl-talk
> *Betreff:* Re: [ncl-talk] mean value of all displayed grid points / pixel
> in a map
>
>
>
> As previously noted:
>
> For a rectilinear grid: wgt_areaave_Wrap calculates an area average
>
> https://www.ncl.ucar.edu/Document/Functions/Contributed/wgt_areaave_Wrap.shtml
>
> For a curvilinear grid:
> http://www.ncl.ucar.edu/Document/Functions/Built-in/wgt_areaave2.shtml
>
> or a simple arithmetic average: avg
>
> http://www.ncl.ucar.edu/Document/Functions/Built-in/avg.shtml
>
>
>
>
>
>
>
> On Mon, Sep 1, 2014 at 7:57 AM, Kreienkamp Frank <Frank.Kreienkamp at dwd.de>
> wrote:
>
> Hello Dennis,
>
>
>
> sorry that my question wasn’t clear enough.
>
>
>
> Let my try again.
>
> The attached map is a displayed result of RCM-dataset. The original grid
> covers Europe. The displayed area covers Germany and a bit more.
>
>
>
> What I am looking for is a routine that calculates the mean value of the
> displayed area.
>
>
>
> Thanks in advance
>
> Frank
>
>
>
> *Von:* ncl-talk-bounces at ucar.edu [mailto:ncl-talk-bounces at ucar.edu] *Im
> Auftrag von *Dennis Shea
> *Gesendet:* Montag, 1. September 2014 15:11
> *An:* Kreienkamp Frank
> *Cc:* ncl-talk
> *Betreff:* Re: [ncl-talk] mean value of all displayed grid points / pixel
> in a map
>
>
>
> The question is vague
>
> "I want to calculate the mean value of all displayed grid points in a map.
>
> This means:
> - i have gridded data for the entire world (gcm-results)
> - i plot a map (stereographic projection) for Europe
>
> NCL draws a rectangle map based on the given resource parameters. I am
> looking for a function which counts all displayed values (pixel?) and
> calculates an average value."
>
> NCL handles "gridded data for the entire world (gcm-results)" all the time.
>
>
>
> [1]  dim_avg_n_Wrap will calculate the means at each grid point over all
> times.
>
> [2] wgt_areaave_Wrap calculates an area average
>
> [3] NCL can display much more than a "rectangular map"
>
> [4] wks = gsn_open_wks("png" ,"frank")
>
>      will send graphics to a png file
>
> What do you mean by:
>
> "Is there a chance that i can get the matrix-values which are send to the
> (png-)workstation?"
>
>
> =======
>
> https://www.ncl.ucar.edu/Document/Functions/Contributed/dim_avg_n_Wrap.shtml
> https://www.ncl.ucar.edu/Applications/climo.shtml
>
> https://www.ncl.ucar.edu/Document/Functions/Contributed/wgt_areaave_Wrap.shtml
> https://www.ncl.ucar.edu/Applications/maponly.shtml
>
> https://www.ncl.ucar.edu/Document/Graphics/Interfaces/gsn_csm_contour_map.shtml
>
> Good luck
>
>
>
> On Mon, Sep 1, 2014 at 2:31 AM, Kreienkamp Frank <Frank.Kreienkamp at dwd.de>
> wrote:
>
> Hello ,
>
> since having no one answering the original question.
>
> Is there a chance that i can get the matrix-values which are send to the
> (png-)workstation?
>
> Thanks in advance
> Frank Kreienkamp
>
> -----Ursprüngliche Nachricht-----
> Von: ncl-talk-bounces at ucar.edu [mailto:ncl-talk-bounces at ucar.edu] Im
> Auftrag von Frank Kreienkamp
> Gesendet: Mittwoch, 27. August 2014 06:37
> An: ncl-talk
> Betreff: [ncl-talk] mean value of all displayed grid points / pixel in a
> map
>
>
> Hello,
>
> i have searched the function list but i have not found a solution for the
> following problem.
>
> I want to calculate the mean value of all displayed grid points in a map.
>
> This means:
> - i have gridded data for the entire world (gcm-results)
> - i plot a map (stereographic projection) for Europe
>
> NCL draws a rectangle map based on the given resource parameters. I am
> looking for a function which counts all displayed values (pixel?) and
> calculates an average value.
>
> Thanks in advance
> Frank
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