[R-sig-Geo] plot extent and/or convert extent to SpatialPolygons

[Agustin Lobo]

Apologies.
I had done
ext128 <- c(128,1280-128,128,960-128)

instead of
ext128 <- extent(c(128,1280-128,128,960-128))

This is why plot() and as() were not working for me.
Agus

On Mon, Sep 21, 2015 at 10:31 AM, John Baumgartner <johnbaums at gmail.com> wrote:
> I just realised my reply only went to Agustin - here it is again...
>
> You can convert extent e to SpatialPolygons with
>
> as(e, 'SpatialPolygons')
>
> ... but yes, you can also plot the extent object with plot.
>
> e.g.
>
> r <- raster(matrix(runif(100), nc=10))
> plot(r)
> e <- extent(0.5, 0.75, 0.5, 0.75)
> plot(e, add=TRUE)
>
> On Mon, Sep 21, 2015 at 6:29 PM, Manuel Schneider <
> manuel.schneider at agroscope.admin.ch> wrote:
>
>> Agustin Lobo <alobolistas <at> gmail.com> writes:
>>
>> >
>> > Is it possible to plot an extent object (i.e. on top of a raster like
>> > it would be done for a polygon with add=TRUE)
>> > Or can I just convert the extent object to SpatialPolygons?
>> >
>> > Thanks
>> > Agus
>> >
>>
>> Try
>>
>> bbox2square <- function(bb)
>> {
>>         coord.mat <- data.frame(x=rep(bb[1,],each=2),y=c(bb[2,],bb[2,2:1]))
>>         coord.mat <- rbind(coord.mat, coord.mat[1,])
>>         sq <- SpatialPolygons(list(Polygons(list(Polygon(coord.mat)), ID =
>> 1)))
>>         return(as(sq, "SpatialPolygonsDataFrame"))
>> }
>>
>> where bb <- bbox(obj)
>>
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