听起来这就是你想要的:
plot(mtcars[3:4])
title(main = "My Plot")
mysubtitle = "Subtitle here"
anothersubtitle = "Another subtitle here"
mtext(side = 3, line = 0.25, at = 1, adj = -2, mysubtitle)
mtext(side = 2, line = 2, anothersubtitle)
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