quadratcount(X, nx=5, ny=nx, xbreaks, ybreaks)
"ppp"
).xbreaks
and ybreaks
.nx
.ny
.X
is divided into
an nx * ny
grid of rectangular tiles or `quadrats'.
The number of points of X
falling in each quadrat is
counted. These numbers are returned as a contingency table. If xbreaks
is given, it should be a numeric vector
giving the $x$ coordinates of the quadrat boundaries.
If it is not given, it defaults to a
sequence of nx+1
values equally spaced
over the range of $x$ coordinates in the window X$window
.
Similarly if ybreaks
is given, it should be a numeric
vector giving the $y$ coordinates of the quadrat boundaries.
It defaults to a vector of ny+1
values
equally spaced over the range of $y$ coordinates in the window.
The lengths of xbreaks
and ybreaks
may be different.
The algorithm counts the number of points of X
falling in each quadrat, and returns these counts as a
contingency table. The [i,j]
entry in the contingency table
is the point count for the quadrat with coordinates
(xbreaks[i],xbreaks[i+1])
by (ybreaks[i], ybreaks[i+1])
.
Stoyan, D. and Stoyan, H. (1994) Fractals, random shapes and point fields: methods of geometrical statistics. John Wiley and Sons.
X <- runifpoint(50)
quadratcount(X)
quadratcount(X, 4, 5)
quadratcount(X, xbreaks=c(0, 0.3, 1), ybreaks=c(0, 0.4, 0.8, 1))
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