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Am doing some vector plots with the arrows() function. Works well. But what I need to do is supply an arrow for scaling for the reader. I need to plot an arrow of some known magnitude somewhere on the page (preferably outside the bounds of the plot, so that it can be seen clearly) with some text underneath it that says, for instance, "10 kg-m/sec". Any ideas? Thanks.

Do you know what steps I need to take to add a scale to a plot? I'm pulling my example out of "An Introduction to R: Software for StatisticalModelling & Computing" (see the R code around Figure 76). I would like to add a scale to the image produced by the following code.? I would like to the scale to list the distance?and units:? data(volcano) x <- 10*(1:nrow(volcano)) y