If 'X' is a data frame containing columns 'x', 'y' and 'value, try
m <- with(X, tapply(value, list(y,x), all))
z <- im(m, xcol=sort(unique(X$x)), yrow=sort(unique(X$y)))
w <- as.owin(z)
This will only work if the x, y values form a rectangular grid in some
order.
Adrian Baddeley
=============================================
Javier PB wrote:
Dear users,
I am trying to export polygons from Arcmap into Spatstat to run some
simulations using functions available in Spatstat package.
One particular area to be exported is formed by a number of polygons
defining the external boundaries of the area (as a groups of islands)
and a
number of polygons inside the previous ones, as “holes” not to be
considered as part of the area.
I have managed to export one of these areas using owin(poly=list()),
including in the list the number of external boundaries and holes,
but the
number of polygons that constitute each area is large and I was
wondering if
this could be easily done using owin(mask=my_area), using only one
single
matrix file "my_area" with TRUE, FALSE values defining the whole area.
Here is where I got stuck. The file I have created in ArcMap contains
three
columns: x and y coordinates, and the values at points x[i], y[j] (1
if the
area is TRUE and 0 is the area is FALSE).
How can I covert this xy file into a mask type "my_area" that I can read
using owin(mask=my_area)?
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