Hi all,
I am using quadratcount in spatstat to divide a window containing a
point pattern into a grid of quadrats containing the intensity of points
in each quadrat. My data is in UTM co-ordinates. My window is defined
as follows:
>p15<-ppp(x,y,window=owin(c(341710,342100),c(3126465,3126780)),marks=NUL
L, checks=TRUE)
Giving me a distance of 390m in the 'x' direction and 315m in the 'y'
direction. I want to divide the window into quadrats of size 15m x 15m
so I did the following:
>q15<-quadratcount(p15,nx=26,ny=21).
However, when I look at the data for quadrat counts it seems the
function is not keeping the size of the quadrats constant, but is
instead varying the width of the quadrats (in both the x and y
direction) between 10m and 20m, meaning that some quadrats are 10m x 10m
and some are four times the size (20m x 20m) (I have pasted some of the
output below to demonstrate). This is quite concerning as I am trying
to ascertain the scale of variation in my point pattern density - I
cannot do this if the quadrat scale does not stay constant!!
Does anyone know how to make quadratcount produce equally sized
quadrats?
Many thanks
Lauren
ymin 3126470 3126480 3126500 3126510 3126530
ymax 3126480 3126500 3126510 3126530 3126540
xmin xmax
341710 341720 0 1 0 0 0
341720 341740 0 0 3 1 5
341740 341750 0 1 2 1 3
341750 341770 2 1 0 0 1
341770 341780 4 6 5 4 0
341780 341800 1 4 2 1 1
341800 341810 0 0 1 5 1
341810 341830 0 0 0 1 3
341830 341840 4 1 3 0 0
341840 341860 1 1 0 0 2
341860 341880 4 2 0 0 3
341880 341890 3 2 0 5 1
341890 341900 3 2 0 4 1
341900 341920 3 2 2 0 0
341920 341930 0 3 2 3 0
341930 341950 1 5 2 2 4
341950 341960 0 0 6 3 2
341960 341980 0 0 0 3 2
341980 341990 0 0 0 0 0
341990 342010 0 0 3 0 0
342010 342020 1 0 0 0 0
342020 342040 1 1 1 1 2
342040 342050 1 0 0 0 2
342050 342070 1 0 0 0 0
342070 342080 1 0 0 0 0
342080 342100 0 0 0 0 0
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