Re: [ferret_users] surface plot - using POLYGON

To: nag_ocean005@xxxxxxxxxxx
Subject: Re: [ferret_users] surface plot - using POLYGON
From: mick spillane <mick.spillane@xxxxxxxx>
Date: Tue, 16 Dec 2008 14:30:36 -0800
Cc: Ferret NOAA <oar.pmel.ferret_users@xxxxxxxx>
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Hi Golla,

Here is a method that might work for you. The type of result isshown in the attached image where I've used the Smith-Sandwellbathymetry as a background on which to plot strips showing the surfacetemperature (from Levitus) along each of 5 zonal sections.

   Hope it helps,
      Mick

PS There are other ways to do it of course. There is the POLYMARKscript, or you could just write the surface temperatures to an ASCIIfile on a suitable grid, with missing values where necessary, then readthe file back and use SHADE. But if you get used to POLYGON it turnsout to be very flexible for generating other plots ... like histograms.

--------------------------------------

Step 1: Read in your 5 datasets and determine the range of latitude andlongitude needed to include them all, and also the overall range oftemperature at the depth level you want. For the demo I've extracteddata from the Levitus climatology so each point represents a 1x1 degreearea of the variable "temp"


use zone1.nc ; use zone2.nc ; use zone3.nc ; use zone4.nc ; use zone5.nc
let t0=temp[k=1]    ! temperature at  the depth you require
set data 1 ; sho grid/all temp ; list/nohead t0[x=@min],t0[x=@max]
...
set data 5 ; sho grid/all temp ; list/nohead t0[x=@min],t0[x=@max]

Step 2: Make the background plot - bathymetry with suitable aspect ratio

use smith_sandwell_topo  ! or some other topo file you use
ppl axlen,12,7.565 ; ppl size,14,9.565 ; ppl origin,1,1

shade/nolab/pal=dark_land_sea/lev=(-10000,10000,500)(-500,500,100)/x=180:220/y=-5:20rose

Step 3 : Each value is going to appear as a colored rectangle, centeredon the lat,lon of the point it represents, so what we need is to definethe center points ...


let xx=x[g=t0] ; let yy=y[g=t0]

... and increments to the vertices (in my case a 1x1 box) surroundingthem. In your case, different increments in X and Y might be appropriate(there are ways using XBOXLO... to generalize the process though thescript gets a bit harder to read)

let bx=tsequence({-0.5,0.5,0.5,-0.5}) ; letby=tsequence({-0.5,-0.5,0.5,0.5})

(The four vertices were defined as a t-axis variable because thedatasets use x,y and z axes.)

Step 4: Now we are ready to go. Use the first point of the firstsection to make the colorbar ...

here drawn across the top ...

set data 1

poly/o/nolab/pal=inverse_redscale/lev=(24.8,28.1,0.1)/coord=t/key/i=1/setxx+bx,yy+by,t0

ppl shakey,,0 ; ppl fillpoly/over

then draw then entire set of 21 points for section#1