[R] vectors on top of contours, and lattice

[Deepayan Sarkar]

On 4/8/09, Cable, Samuel B Civ USAF AFMC AFRL/RVBXI
<Samuel.Cable at hanscom.af.mil> wrote:
> OK, I needed to plot a set of vectors on top of a contour plot.  I
>  figured out a way to do this.  I create a panel function that calls
>  "larrows()" with arguments constructed from my vector data.  Then, when
>  I go to do the contour plot, I call contourplot() with the "panel"
>  argument set to point to my newly created panel function.
>
>
>
>  So far, so good.
>
>
>
>  Now, I need to do a series of contour plots, each overlaid with a
>  different set of vectors.  I can call contourplot(z~x*y,...)  but now
>  I'm stuck, because each contour plot will be overlaid with the *same*
>  vector plot.  This won't work because each set of contoured data has its
>  own particular set of associated vector data.  (BTW, I am not doing
>  gradients here.  The vector data is its own entity, not derivable from
>  the contoured data.)  Can I somehow define a whole series of panel
>  functions and coax contourplot() to choose the right one for each of its
>  plots?  Or do I have to revise my entire approach here?

See ?packet.number for one approach. This should allow you to extract
the correct component of the vector data inside the panel function.

-Deepayan