Le 28/07/2019 à 17:08, Roger Bivand a écrit : This feels like a
section in
ASDAR, ch. 3, and code chunks 24-27 in
https://asdar-book.org/book2ed/vis_mod.R. Could you please try that
first
by way of something reproducible?
Le 28/07/2019 à 17:15, Patrick Giraudoux a écrit :
Ups... How can I have missed this chapter of my bible ;-) ? (must
admit I
had been on google first). Will re-read it carefully and come back
to the
list with a solution or a reproducible example, indeed.
OK. Read it again, I was not totally lost. Here is a reproducible
example. To ease reproducibility with simple objects, I will use two
bounding boxes. bbChina in WGS84, bbChinaUTM47 in UTM47. I want a
window fitting the WGS84, and you'll see I get it through a strange way.
bbChina <- new("SpatialPolygons", polygons = list(new("Polygons",
Polygons = list( new("Polygon", labpt = c(104.8, 35.95), area =
2372.28, hole = FALSE, ringDir = 1L, coords = structure(c(73, 73,
136.6, 136.6, 73, 17.3, 54.6, 54.6, 17.3, 17.3), .Dim = c(5L, 2L)))),
plotOrder = 1L, labpt = c(104.8, 35.95), ID = "1", area = 2372.28)),
plotOrder = 1L, bbox = structure(c(73, 17.3, 136.6, 54.6), .Dim =
c(2L, 2L), .Dimnames = list(c("x", "y"), c("min", "max"))),
proj4string = new("CRS", projargs = "+init=epsg:4326 +proj=longlat
+datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0"))
bbChinaUTM47 <- new("SpatialPolygons", polygons =
list(new("Polygons", Polygons = list( new("Polygon", labpt =
c(856106.391943348, 4317264.60126758 ), area = 30651262771540.1, hole
= FALSE, ringDir = 1L, coords = structure(c(-2331000.09677063,
-2331000.09677063, 4043212.88065733, 4043212.88065733,
-2331000.09677063, 1912947.1678777, 6721582.03465746,
6721582.03465746, 1912947.1678777, 1912947.1678777), .Dim = c(5L,
2L)))), plotOrder = 1L, labpt = c(856106.391943348,
4317264.60126758), ID = "1", area = 30651262771540.1)), plotOrder =
1L, bbox = structure(c(-2331000.09677063, 1912947.1678777,
4043212.88065733, 6721582.03465746), .Dim = c(2L, 2L), .Dimnames =
list(c("x", "y"), c("min", "max"))), proj4string = new("CRS",
projargs = "+init=epsg:4326 +proj=longlat +datum=WGS84 +no_defs
+ellps=WGS84 +towgs84=0,0,0"))
Then let's go:
Example #1: here, being straightforward we get two indesirable white
strips on the sides:
width1<-max(bbox(bbChina)[1,])-min(bbox(bbChina)[1,])
height1<-max(bbox(bbChina)[2,])-min(bbox(bbChina)[2,])
ratio<-width1/height1
ratio
windows(height=8,width=8*ratio)
par(mar=c(0,0,0,0))
plot(bbChina,col="grey",xaxs='i', yaxs='i')
dev.off()
Example #2: computing the ratio on UTM47, but plotting WGS84
(strange), I get a better fit but with still two small white strips
up and down.
width1<-max(bbox(bbChinaUTM47)[1,])-min(bbox(bbChinaUTM47)[1,])
height1<-max(bbox(bbChinaUTM47)[2,])-min(bbox(bbChinaUTM47)[2,])
ratio<-width1/height1
ratio
windows(height=8,width=8*ratio)
par(mar=c(0,0,0,0))
plot(bbChina,col="grey",xaxs='i', yaxs='i') # no data range extention
(xaxs and yaxs parameter)
dev.off()
Example #3: multiplying the ratio by 1.04, I get a good fit
width1<-max(bbox(bbChinaUTM47)[1,])-min(bbox(bbChinaUTM47)[1,])
height1<-max(bbox(bbChinaUTM47)[2,])-min(bbox(bbChinaUTM47)[2,])
ratio<-width1/height1
ratio
windows(height=8,width=8*ratio*1.04)
par(mar=c(0,0,0,0))
plot(bbChina,col="grey",xaxs='i', yaxs='i')
dev.off()
Looks like the issue has something to do with the way CRS are handled
when plotting objects, mmmh ? Tricky isn't it ?
