How to plot segments or arrows with Lattice in R? (from a Wide format dataset)

Question

I would like to create a plot with segements or arrows.

Let\'s say I have this toy example

temp <- data.frame(posi=c(1,2,3,3,2,1,5), from=c(\"A\",         


        

Answer 1

You could use the following code:

xyplot(from ~ posi , type="p", col="black",  data=temp, pch=16, xlim = c(0,7),
       panel = function(...){
         panel.dotplot(x = (temp$posi+1), y = temp$to, col="black", cex=1.4)
         panel.dotplot(x = temp$posi, y = temp$from, col ="black", cex=1.4)
         panel.arrows(x0 = temp$posi, y0 = temp$from, x1 = temp$posi+1, y1 = temp$to, lwd=3, col="blue", )
       }
)

yielding the following graph:

Please let me know whether this is what you want.

UPDATE

I posted a question concerning the problem that @skan identified and described in the comments: when a "extreme" level (like "D") is not present in temp$from then the "D" will not part of the graph, even when "D" will be needed later for temp$to. The question with answer from @Konn may be found here.

As I understand it now, we need a factor that is ordered, and we need an addition to the code specifying drop.unused.levels = FALSE in the call to xyplot. In the example we show the full set with "extremes" in "from" and as subset where the extreme "D" is absent: The full code is:

l <- c("A", "B", "C", "D")
temp <- data.frame(posi = c(1, 2, 3, 3, 2), 
                   from= factor(c("A", "B", "C", "D", "D"), levels = l, ordered = TRUE),
                   to = factor(c("C", "D", "D", "C", "A"), levels = l, ordered = TRUE)
                   ) 


xyplot(from ~ posi , type="p", col="black",  data=temp, pch=16, xlim = c(0,7), 
       drop.unused.levels = FALSE,  ## the added code
       panel = function(...){
         panel.dotplot(x = temp$posi, y = temp$from, col ="green", cex=1.6)
         panel.dotplot(x = (temp$posi+1), y = temp$to, col="black", cex=1.)
         panel.arrows(x0 = temp$posi, y0 = temp$from, x1 = temp$posi+1, y1 = temp$to, lwd=2, col="blue" )
       })

temp <- temp[1:3, ]
xyplot(from ~ posi , type="p", col="black",  data=temp, pch=16, xlim = c(0,7), 
       drop.unused.levels = FALSE,  ## the added code
       panel = function(...){
         panel.dotplot(x = temp$posi, y = temp$from, col ="green", cex=1.6)
         panel.dotplot(x = (temp$posi+1), y = temp$to, col="black", cex=1.)
         panel.arrows(x0 = temp$posi, y0 = temp$from, x1 = temp$posi+1, y1 = temp$to, lwd=2, col="blue" )
       })

yielding the following pics:

I think we have solved this question.