interp.im
From spatstat v1.41-1
by Adrian Baddeley
Interpolate a Pixel Image
Interpolates the values of a pixel image at any desired location in the frame.
Usage
interp.im(Z, x, y=NULL)
Arguments
- Z
- Pixel image (object of class
"im"
) with numeric or integer values. - x,y
- Vectors of Cartesian coordinates.
Alternatively
x
can be a point pattern andy
can be missing.
Details
A value at each location (x[i],y[i])
will be
interpolated using the pixel values of Z
at the four
surrounding pixel centres, by simple bilinear interpolation.
At the boundary (where (x[i],y[i])
is not surrounded by
four pixel centres) the value at the nearest pixel
is taken.
The arguments x,y
can be anything acceptable to
xy.coords
.
Value
- Vector of interpolated values, with
NA
for points that lie outside the domain of the image.
Examples
opa <- par(mfrow=c(1,2))
# coarse image
V <- as.im(function(x,y) { x^2 + y }, owin(), dimyx=10)
plot(V, main="coarse image", col=terrain.colors(256))
# lookup value at location (0.5,0.5)
V[list(x=0.5,y=0.5)]
# interpolated value at location (0.5,0.5)
interp.im(V, 0.5, 0.5)
# true value is 0.75
# how to obtain an interpolated image at a desired resolution
U <- as.im(interp.im, W=owin(), Z=V, dimyx=256)
plot(U, main="interpolated image", col=terrain.colors(256))
par(opa)
Community examples
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