R help - Sep 2004 - locator() in a multi-figure setting using mfrow()

Hi

based on some code from Thomas Petzoldt (see below), I have a question, 
about how to use locator() in a mfrow() multi-figure setting. I am sure 
this should be a kind of problem, which other people face too?

we have 8 matrices each 10x10 fields, plotted as mfrow = c(2,4).

how can I get, using locator(), the correct index of a field of one of 
the 8 matrices? means, I should get 3 values: the matrix I am in (a 
value between 1..8), and the corresponding x and y coordinates (each in 
1..10)

many, thanks for your kind help.

---
opar <- par(mfrow = c(2,4))
slices <- 8
m <- matrix(runif(100),10,10)
my.list <- list()
for (slice in 1:slices) {
     my.list[[slice]] <- m
}

for  (slice in 1:slices) {
     x <- 1*(1:25)
     y <- 1*(1:25)
     z <- my.list[[slice]]
     image(list(x = 0:9, y = 0:9, z = z))
}
par(opar) #restore device parameters


p <- locator(1)
c(round(p$x), round(p$y))
---

how can I get the "correct" location in the sense of a
3d info: (a) which slice (p$slice) (b) p$x (c) p$y

so that it could be used in the sense of:

	my.list[[p$slice]][round(p$x), round(p$y)]


christoph

I know, that I can use par(mfg = c(i,u)) to get the correct x,y 
coordinates of one of the 8 matrices/subimages, but how can I get the i 
and the j, means how can I know in which of the 8 images I am clicking in?

thanks

Christoph

Christoph Lehmann wrote:
> Hi
> 
> based on some code from Thomas Petzoldt (see below), I have a question, 
> about how to use locator() in a mfrow() multi-figure setting. I am sure 
> this should be a kind of problem, which other people face too?
> 
> we have 8 matrices each 10x10 fields, plotted as mfrow = c(2,4).
> 
> how can I get, using locator(), the correct index of a field of one of 
> the 8 matrices? means, I should get 3 values: the matrix I am in (a 
> value between 1..8), and the corresponding x and y coordinates (each in 
> 1..10)
> 
> many, thanks for your kind help.
> 
> ---
> opar <- par(mfrow = c(2,4))
> slices <- 8
> m <- matrix(runif(100),10,10)
> my.list <- list()
> for (slice in 1:slices) {
>     my.list[[slice]] <- m
> }
> 
> for  (slice in 1:slices) {
>     x <- 1*(1:25)
>     y <- 1*(1:25)
>     z <- my.list[[slice]]
>     image(list(x = 0:9, y = 0:9, z = z))
> }
> par(opar) #restore device parameters
> 
> 
> p <- locator(1)
> c(round(p$x), round(p$y))
> ---
> 
> how can I get the "correct" location in the sense of a
> 3d info: (a) which slice (p$slice) (b) p$x (c) p$y
> 
> so that it could be used in the sense of:
> 
>     my.list[[p$slice]][round(p$x), round(p$y)]
> 
> 
> christoph
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! 
> http://www.R-project.org/posting-guide.html
> 
>

thanks to some great hints by Paul Murrel I could solve it: here we are 
with one solution (code needs to be cleaned and simplified, but maybe 
one can understand it)

#######
## create a multifigure setting
nr <- 4
nc <- 2
opar <- par(mfrow = c(nr, nc))
slices <- 8
m <- matrix(runif(100),10,10)
my.list <- list()
for (slice in 1:slices) {
     my.list[[slice]] <- m
}

for  (slice in 1:slices) {
     x <- 1*(1:25)
     y <- 1*(1:25)
     z <- my.list[[slice]]
     image(list(x = 0:9, y = 0:9, z = z))
}
########
my.get.coord <- function() {
par(mfg = c(1,1)) #locator() shall be relative to the first plot out
# of the eight plots totally
my.loc <-locator(1) #location, not in inches
my.plot.region <- par("usr") #extremes of plotting region
#(in plot units, not inches)
my.plot.region.x <- my.plot.region[2] - my.plot.region[1]
my.plot.region.y <- my.plot.region[4] - my.plot.region[3]
my.loc.inch.x <- (my.loc$x + 0.5)/my.plot.region.x *
(par("pin")[1])
#par("pin") #current plot dimension in inches
#relative to the plotting-region bottom left corner, not the axis c(0,0) 
point
my.loc.inch.y <- (my.loc$y + 0.5)/my.plot.region.y *
(par("pin")[2])

## search the plot we are in with locator(1)
my.plot.inch.x <- par("pin")[1] + par("mai")[2] +
par("mai")[4] #plot.x
+ left & right margin
par("fin")[1]
my.plot.inch.y <- par("pin")[2] + par("mai")[1] +
par("mai")[3] #plot.y
+ bottom & top margin
par("fin")[2]

pos.rel.x <- (my.loc.inch.x / par("fin")[1] - floor(my.loc.inch.x /
par("fin")[1])) *
      par("fin")[1] / par("pin")[1] *
(par("usr")[2] - par("usr")[1]) - 0.5
      #inches from left bottom corner in target plot region (c(0,0)
      # is plot-region bottom-left corner, not the axis c(0,0) point
pos.rel.y <- (my.loc.inch.y / par("fin")[2] - floor(my.loc.inch.y /
par("fin")[2])) *
      par("fin")[2] / par("pin")[2] *
(par("usr")[4] - par("usr")[3]) - 0.5
      #inches from left bottom corner in target plot

fig.coord.x <- ceiling(my.loc.inch.x / par("fin")[1])
fig.coord.y <- 1 +(-1) *ceiling(my.loc.inch.y / par("fin")[2])
# cat("figure-coord x: ", fig.coord.x,"\n")
# cat("figure-coord y: ", fig.coord.y,"\n")
cat("we are in figure: ", fig.coord.y * nc + fig.coord.x,
"\n")
cat("coordinates of the identified point x: ",
round(pos.rel.x),"\n")
cat("coordinates of the identified point y: ",
round(pos.rel.y),"\n")
}

########
my.get.coord()


Christoph