Hi Greg,
The assignment operation only creates a new reference to the original
object. I have long thought a "dup" method would be useful for HLU
objects, but it does not exist now, and, as far as I know, there have not
been many requests for it (so far).
-dave
On Fri, 28 Mar 2003, Greg Thompson wrote:
>
> Could someone help me diagnose a problem I'm having when overlaying
> wind vectors on a wind-speed contour plot? Here's what I'm trying
> to do.
>
> 1. create a wind speed contour object called "cn_wspd"
> 2. create a duplicate of cn_wspd as "cn_wspd2"
> 3. create wind barb (vector) object called "wind_vectors"
> 4. create a graphic with wind_vectors overlayed on cn_wspd2
>
> I can accomplish this just fine. Now for the problem.
>
> 5. advance frame
> 6. create a streamline object called "streams"
> 7. overlay streams on top of the original "cn_wspd" (the copy
> of wind speed that SHOULD not contain wind barbs). Yet
> my final graphic shows both the wind barbs and the streamlines
> as if I'm overlaying streams onto cn_wspd2.
>
> Here's my code snipet:
>
> cn_wspd2 = cn_wspd
> overlay(cn_wspd2, wind_vectors)
> draw(cn_wspd2)
>
> frame(wks)
>
> overlay(cn_wspd, streams)
> draw(cn_wspd)
>
> The second draw produces both overlays as if cn_wspd already had
> the wind_vectors object overlayed. Why? Isn't "cn_wspd2" a
> total copy of "cn_wspd" and independent?
>
> Thanks.
>
> -- Greg T. NCAR/RAP
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