Adding Points to filled.contour in R - at the right place

Question

I'd like to add a point to an existing filled.contour plot, using the following code:

MyFunction <- function(x,y){
   return(dnorm(sqrt(x^2+y^2)))
}
wrapper <- function(x, y, my.fun, ...) {sapply(seq_along(x), FUN = function(i) my.fun(x[i], y[i], ...))}
meshstep <- 0.5
x<- seq(-20,20,meshstep)
y <-seq(-20,20,meshstep)
z <- outer(x,y,FUN = wrapper, my.fun=MyFunction)
filled.contour(x,y,z, col=rev(heat.colors(n=20, alpha=0.7)), nlevels=15)
points(0,0)

I'm pretty surprised that points(0,0) didn't put a point into the origin of the plot, but roughly located at x=10,y=0. Also, locator() seems to be prompting coordinates with respect to that 'new' coordinate system as well. Why is that?

This question has some overlap with the link provided by juba. Since I'm looking to make `locator()` work, I hope this merits not closing it. — Roland, Oct 17 '13 at 19:42

score 4 · Answer 1 · edited May 23 '17 at 12:14

4

You can find a detailed answer here : Plotting a box within filled.contour plots in R?

In short, filled.contour use two different coordinates system, one for the filled contour and one for the legend. To solve your problem, you either have to use another function, or to put your points into the plot.axes argument :

filled.contour(x,y,z, col=rev(heat.colors(n=20, alpha=0.7)), nlevels=15,
               plot.axes={points(0,0)})

enter image description here

edited May 23 '17 at 12:14

Community

1
1

answered Oct 17 '13 at 14:32

juba

47,631
14
113
118

Do you have an idea how to make `locator()` work with `filled.contour`? – Roland Oct 17 '13 at 16:43
I'm not sure it is possible, given the two scales problem. Maybe you should try another function ? – juba Oct 17 '13 at 17:26

score 2 · Accepted Answer · answered Oct 17 '13 at 17:41

The best option is to use the plot.axes argument as mentioned by @juba. But, if you really need to add something after the plot has finished then you can use locator to click on 2 points in the plot where you know the values of the points in the coordinate system you want to use (opposite corners), then use the updateusr function from the TeachingDemos package to modify the current coordinate system to the one that you want to use. You can then add to the plot using the new coordinate system (you may need to set par(xpd=NA)).

Adding Points to filled.contour in R - at the right place

2 Answers2

Linked