Too many open devices r

You are supposed to put your jpeg command before you call your plot command.

jpeg(file=mypath)
plot(...)
dev.off()

Combination of the answers from Mohammed Shaker and asb gives this really simple code:

for (i in dev.list()[1]:dev.list()[length(dev.list())]) {
   dev.off()
}

This removes all open graphics devices:

> dev.list()
NULL

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