Analysing spatial point patterns in R - CSIRO

D
y
66 Pixel images in spatstat
Z
print basic information
print(Z) print basic information
summary(Z) print detailed information
dim(Z) pixel raster dimensions (y,x)
nrow(Z) number of rows (y coordinate)
ncol(Z) number of columns (x coordinate)
range(Z) range of pixel values
max(Z) maximum of pixel values
min(Z) minimum of pixel values
mean(Z) mean of pixel values
median(Z) median of pixel values
quantile(Z, ...) quantiles of pixel values
sum(Z) sum of pixel values
integral.im(Z) sum of pixel values times pixel area
To compute other numerical summaries of pixel values that are not on this list, you can
extract the pixel values using as.matrix(Z) then apply the desired operation.
10.2.2 Plotting an image
Methods for plotting an image object include:
plot.im display as colour image
contour.im contour plot
persp.im perspective plot of surface
These are methods for generic functions, so you would typeplot(Z),contour(Z) orpersp(Z)
to display a pixel image Z.
> opa data(redwood)
> D plot(D)
> persp(D)
> contour(D)
> par(opa)
D
D
D
0 20 40 60 80 100 120
x
−1.0 −0.8 −0.6 −0.4 −0.2 0.0
50
30
10
20
60
40
20
40
60
90
110
120
100
30
70
80
110
100
50
70
70
60
70
100
80
110
120
30
40
90
50
60
70
50
40
80
0.0 0.2 0.4 0.6 0.8 1.0
For plot.im, note that the default colour map for image plots in R has only 12 colours
and can convey a misleading impression of the gradation of pixel values in the image. Use the
argument col to control the colour map.
> opa plot(D)
CopyrightCSIRO 2010