Setting R plot xlim with only the lower bound

Question

Suppose I have created a simple plot like this:

xvalues <- 100:200
yvalues <- 250:350
plot(xvalues, yvalues)

However, I would like the x-axis to start at 0 and leave the upper bound to be whatever is computed by R. How can I do this?

I know there is an option for xlim=c(lower bound, upper bound), but I don't know what the upper bound is. Also, I am evidently unable to let the upper bound be unspecified:

> plot(xvalues, yvalues, xlim=c(0))
Error in plot.window(...) : invalid 'xlim' value

It would be great if I didn't have to compute the max value of the xvalues vector in order to get the upper bound, as that seems wasteful for a very large data vector.

Answer 1

You could use one of two approaches:

Calculating the limits

xlim <- c(0, max(xvalues))

xlim can now be supplied as the xlimargument in plot.

xvalues <- 100:200
yvalues <- 250:350
plot(xvalues, yvalues, xlim=xlim)

Let par return the limits

This one is a bit more sophisticated, but sometimes helpful (certainly overkill in your case, but for completeness). You plot the data once, you get the limits of the plotting area in user coordinates using par("usr"). Now you can use these in your new plot.

plot(xvalues, yvalues, xaxs="i")
xmax <- par("usr")[2]
plot(xvalues, yvalues, xlim=c(0,xmax))

PS. I used xaxs="i" so the results will be without small extensions at the ends.

Answer 2

you can simply set the max for x using the max of you values:

xvalues <- 1:99
yvalues <- rep(1,99)


plot(xvalues, yvalues, xlim = c(0, max(xvalues)) )