Dear all,

I have a data set which has latitude, longitude (not in increasing order)
and observed precipitation corresponding to those locations. I am using
image.plot command for that. But I want to overlay a map of US on that plot.
I know we can use map('usa') to draw it, but I dont know how can I overlay
it on the plot of the precipitation data. Can anyone please help me with it?


Thanks in advance.

Cassie.

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