spatstat - affine a window - enlarging (with same center)

Hi List,


I'd like to visually compare two spatial objects of France contour

I have the population in France, the population in the 10 first major
cities and I want to enlarge France by a ratio defined by pop(10 major
cities)/pop(france), sort of a world cartogramwith the transformation of
one country.

But I have problems using shear transformation.

Here is the code for the moment:

fr <- readOGR(".", "FRANCE_METRO")
fr.win <- as(fr, "owin")

pop.fr <- 65447374
townpops <- sum(pop$population)
ratio <- townpops / pop.fr

## here is my problem...
fr.aff <- affine(fr.win,  mat=matrix(c(ratio,0,0,ratio), ncol=2));

Any help would be greatly appreciated


Mathieu

[[alternative HTML version deleted]]

Hi  Mathieu,

Maybe Adrian or Rolf would give a more informated answer, but in the mean
time,  my opinion is that you should compute the centroid of the affined
window and apply a "counter"-shift equivalent to the  shift that
experiments the affined window.

Here's my example with the letterR window (I don't have the
metropolitan France map at hand)

data (letterR)

ratio<- 2 # example "ratio"

letterRa<- affine(letterR, mat=matrix(c(ratio,0,0,ratio), ncol=2))

# centroids of the original and affined windows
cLR<- centroid.owin(letterR)
cLRa<- centroid.owin(letterRa)

# this is the "counter"-shift
LRshift<- c(cLR[[1]]-cLRa[[1]], cLR[[2]]-cLRa[[2]])

# shift the affined window
letterRas<-shift(letterRa, vec=LRshift)

# see the results
plot(letterRas)
plot(letterR, add=T)
points(centroid.owin(letterR))
points(centroid.owin(letterRas), cex=2)

HTH,

Marcelino




Con fecha 22/11/2011, "Mathieu Rajerison"<mathieu.rajerison at gmail.com>
escribi?:

Hi List,


I'd like to visually compare two spatial objects of France contour

I have the population in France, the population in the 10 first major
cities and I want to enlarge France by a ratio defined by pop(10 major
cities)/pop(france), sort of a world cartogramwith the transformation of
one country.

But I have problems using shear transformation.

Here is the code for the moment:

fr<- readOGR(".", "FRANCE_METRO")
fr.win<- as(fr, "owin")

pop.fr<- 65447374
townpops<- sum(pop$population)
ratio<- townpops / pop.fr

## here is my problem...
fr.aff<- affine(fr.win,  mat=matrix(c(ratio,0,0,ratio), ncol=2));

Any help would be greatly appreciated


Mathieu

	[[alternative HTML version deleted]]