Re: Plot buffer size

[verschel@xxxxxxxxxxxxxxxxxxxxx (Mark A. Verschell)]

David,

	This IS a simple (but NOT trivial) problem. Your problem is not with
the calculations but with the display of your results. The underlying PPLUS
package (that handles the graphics) is limited to 495000 points to plot. Now,
when you are doing the vector plot there is no way you will be plotting even
495000 vectors, much less more than that, because the PPLUS vector command will
give you default XSKIP and YSKIP values. But PPLUS calculates the number of
plotting points before the XSKIP and YSKIP are taken into account. Thus, the
error occurs because you could CONCEIVABLY be asking for 832370 points.

So, if you want to look at the whole field, you need to divide the graphic up,
so that you are never passing more than 495000 points to PPLUS. Here is my
suggestion (plus some suggestions for the length and the skips that might look
better):

Instead of:
! Plot the field for verification
vec/length=5.0 txs,tys

Use:
! Plot the field for verification
vec/length=.2/xskip=50/yskip=10/ylim=89s:89n/j=1:178 txs,tys
vec/length=.2/xskip=50/yskip=10/ylim=89s:89n/over/nolab/pen=1/j=179:356 txs,tys
vec/length=.2/xskip=50/yskip=10/ylim=89s:89n/over/nolab/pen=1/j=356:534 txs,tys

Mark Verschell

================================================================================

On Feb 11,  5:05pm, David Oxilia wrote:
> Subject: Plot buffer size
> Ferreters,
>
> I have the feeling this will turn out to be trivial. I want to
> regrid coads winds onto etopo20's grid and then do some
> manipulations on the regridded fields (ie interpolating and
> smoothing). As a check on my procedure I'd also like to plot
> my final fields as a vecor plot.
>
> The code below shows what I'm doing. The script runs fine and
> writes my output fields as desired; however, when I go to
> vector plot these fields I get a:
>
> **ERROR: a program limit has been reached: 832370 points to plot
>           Plot buffer size is: 495000
>
> I'm unclear as to the relationship between the "plot buffer size"
> and allocated memory (which I've set to 15 MWords). I've ran my
> code in diagnostic mode and increased the desperate mode to twice
> the default (hence, 160,000) in hopes that the error is resulting
> from overly splitting the calculation. If anyone can tell me how
> to solve this I'd be grateful.
>
> Thanks, David.
>
> *~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
> David Oxilia			Tel: (541) 737-2368
> COAS:Oregon State University	Fax: (541) 737-2064
> Ocean Admin. Bldg. 104		Email: oxilia@oce.orst.edu
> Corvallis, OR 97331-5503	WWW: http://www.oce.orst.edu/po
> *~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
>
>
> ! Allocate memory for computation
> set memory/size=15			! 1 MWord = 4 MBytes
>
> ! Set data files
> set data etopo20
> set data coads_climatology
>
> ! WIND STRESS
> ! -----------
>
> ! Define wind stress grid as for etopo
> define grid/like=rose[d=1] etopoxy
>
> ! Compute annually averaged wind fields and map to grid
> let uwndt = uwnd[g=etopoxy,l=@ave]
> let vwndt = vwnd[g=etopoxy,l=@ave]
> let wspdt = wspd[g=etopoxy,l=@ave]
>
> ! Set constants
> let c_d = 1.e-3    			! Drag coefficient
> let rho_air = 1.2  			! Density of air in kg/m^3
>
> ! Define (tau_x,tau_y) by filling grid via linear interpolation
> let tx = rho_air*c_d*uwndt[x=@fln:3,y=@fln:3]*wspdt[x=@fln:3,y=@fln:3]
> let ty = rho_air*c_d*vwndt[x=@fln:3,y=@fln:3]*wspdt[x=@fln:3,y=@fln:3]
>
> ! Finally smooth the wind stress with a 5 point boxcar window
> let txs = tx[i=@sbx:5,j=@sbx:5]
> let tys = ty[i=@sbx:5,j=@sbx:5]
>
> ! Plot the field for verification
> vec/length=5.0 txs,tys
>-- End of excerpt from David Oxilia




-- 
 Mark Verschell                     NASA/Goddard Space Flight Center
 verschell@neptune.gsfc.nasa.gov    Code 970/Lab. for Hydrospheric Proc.
 301-614-5669  Fax: 301-614-5666    Greenbelt, MD 20771

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