Plotting outside of the plot area about proc

[xrobin]

One can produce lines outside the plotting area with code like:

roc1 <- roc(aSAH$outcome, aSAH$wfns)
roc2 <- roc(aSAH$outcome, aSAH$ndka)
par(mar=c( 4, 4.5, 1, 1 ))
opa <- par(mar=c(4, 4, 2, 2) + 0.1, mgp = c(2.5, 1, 0))
plot(roc1$specificities, roc1$sensitivities, xlim=c(0.96, 0.66), ylim=c(0.5,0.86), xaxt="n", type="l")
par(opa)
lines(roc2$specificities, roc2$sensitivities)
axis(side=1)

The question remains: why in the previous example the "out of the area" plotting happens only when axis is called between the two calls to plot - it is clearly not the case in this example.

[xrobin]

This is pretty much a minimum reproducible example:

x <- y <- 1:10
smallmar <- rep(0, 4)
bigmar <- c(4, 4, 2, 2)
par(mfrow=c(2, 1))

# First plot outside area
par(mar=bigmar)
plot(x, y, type="n") # l or n doesn't matter - use l to avoid re-plotting
lines(x, y)
par(mar=smallmar)
axis(side=1)
lines(x + 1, y)

# Second plot stays within plot area
par(mar=bigmar)
plot(x, y, type="n")
lines(x, y)
par(mar=smallmar)
lines(x + 1, y)
axis(side=1)

Looks like a bug upstream. If I call axis between the two calls to lines the line extends outside the plot area. It could be a weird clipping effect as described in ?clip: "Exactly when the clipping region will be reset can be hard to predict".

[xrobin]

Long story short, plotting outside the previous plotting area seems to be the normal behaviour when margins are updated (but one has to call axis or box to have it enforced) - after all the plotting area is updated. I do think there is nothing to change here.

Please feel free to re-open if you think otherwise.