[R] using identify() together with plot () and pixmap()
B.Rowlingson at lancaster.ac.uk
Tue Sep 30 10:38:31 CEST 2003
Christoph Lehmann wrote:
> warning: no point with 0.25 inches
> pressing the right mouse button I get:
> what is the problem here and how can I solve it?
The problem is that there is no method for identifying points on a
pixmap (and anyway, you are feeding identify() a matrix).
You'll need to write an "identify.pixmapGrey" function. This would do
something like use the 'locator()' function to get clicks on the screen,
and then it would compute which grid cell the coordinates of those
clicks were in. pixmap objects store enough information for you to work
this out from the attributes - look at the 'bbox' attribute for example.
It would make a nice addition to the pixmap library. Although one
thing that just suprised me was that the different flavours of pixmap -
pixmapGrey, pixmapIndexed, pixmapRGB - dont all inherit from a 'pixmap'
class, which might make it easier to write a single identify function
for all the types.
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