How to change line width of map.scale from package maps? - r

Question

I'm using map.scale() from package maps to create a scale in a map. The following code creates an example of what I'm looking for:
library(maps)
png("example.png", width = 6000, height = 6000)
map(database = "world", regions = 'Brazil',fill = T)
map.scale(-43, -30,
ratio = F,
cex = 9,
lheight= 1,
pos =1,
offset = 1)
dev.off()
As I'm creating a high resolution png image, the line width of the scale produced is not appropriate. You can check it by zooming in the lower right corner of the map.
Is there any parameter that I'm missing to increase the width of the scale?

Answer 1

The reason you can't modify the line width (it's the lwd argument you should be looking for not line height here) is that it isn't applied in the map.scale() function and passed on to the lines() call for that part of the scale. We can, however, programmatically add this functionality to the function by doing something like this:
library(maps)
t <- capture.output(map.scale)
## Strip trailing text:
t <- t[-length(t)]
## Find lines() call and add in a line width argument:
t <- gsub("(lines\\(linexy)", "\\1, lwd=lwd", t)
t <- gsub("(\\.\\.\\.)", "\\1, lwd=10", t)
t <- paste(t, collapse="\n")
eval( parse(text=paste0( "map.scale.new <- ", t )) )
## Use our new map.scale.new() function with lwd= parameter:
png("example.png", width = 6000, height = 6000)
map(database = "world", regions = 'Brazil',fill = T)
map.scale.new(
-43, -30,
ratio = F,
cex = 9,
lwd= 10,
pos =1,
offset = 1
)
dev.off()
You can modify the lwd= to now suit your fancy.