I think it is easiest to describe what I want in terms of the concrete problem I have.
I have data from a number of countries in each of which a sample of people was interviewed. In presenting the results in a forthcoming collaborative publication much emphasis will be placed on the multi-centre nature of the study. Although I suspect colleagues may do this with shaded maps I would prefer to avoid them as (a) they present one fact per country per map (b) they are unfair to the Netherlands and other high density countries.
What I would like to do is to make the background represent Europe (ideally with a map but that is a frill) then place simple scattergrams (or radar plots) on it located roughly where the country is. Another way of describing it might be to say that I want something like the panels produced by lattice but at arbitrary coordinates rather than on a rectangular grid. I suspect I have to do this from scratch and I would welcome hints.
Am I right that there is no off the shelf way to do this?
Is grid the way to go? Looking at the article in Rnews 2(2) and a brief scan of the documentation suggests so. If grid is the way to go then bearing in mind I have never used grid before (a) any hints about the overall possible solution structure would be welcome (b) is this realistic to do within a week or shall I revert to lattice and lose the geography?
Is there a simple way to draw a map in the background? It needs to cover as far as Sweden, Spain and Greece. It can be crude, as long as Italy looks roughly like a boot that is fine. I am an epidemiologist not a geographer.
I received some very helpful hints and was able to get a satisfactory solution. Roger Bivand pointed me in the right way with map. After loading maps and mapproj I go
map("world", region = c("France", "Belgium", "Greece", "Spain", "Italy",
"Switzerland", "Sweden", "Germany", "Netherlands", "Austria",
"Denmark", "Sicily", "Sardinia"),
xlim = c(-10, 30), ylim = c(30, 60),
projection = "albers", parameters = c(30,60), col = "lightgreen")then bearing in mind that my data is in a file called merg which contains the coordinates and the data to plot
merg$x <- mapproject(merg$long,merg$lat)$x merg$y <- mapproject(merg$long,merg$lat)$y
gets the coordinates in the new system. Deepayan Sarkar reminded me about stars which I should have remembered myself from reading MASS. I now go
stars(2*merg[,ord+4], scale = FALSE, len = 0.07, locations = cbind(merg$x,merg$y), labels = NULL, cex = 0.3, key.loc = c(mapproject(-10,60)$x,mapproject(-10,60)$y), add = TRUE )
and get a plot which does what I wanted.
Roger had pointed out that gridbase was probably the way to put scatterplots on the map
but I decided after looking at the stars that scatterplots would end up too small to use
so I stayed with lattice for them.
(When I said scattergrams I meant what nearly everyone else calls scatterplots.)
Thanks to both of them, and to the people who made maps and stars so easy when you know what to look for.
Michael Dewey [EMAIL PROTECTED]
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