[R] Scatter plot - using colour to group points?

SarahH sarah.g10 at hotmail.co.uk
Mon Nov 21 20:17:03 CET 2011

Dear All, 

I am very new to R - trying to teach myself it for some MSc coursework. 

I am plotting temperature data for two different sites over the same time
period which I have downloaded from a university weather station data

I am using the following code to create the plot

plot ( x = TEMP3[,"TIME"], y = TEMP3[,"TEMP"], type = "p", col =
TEMP3[,"SITE"], pch = 3, main = "Temperature changes", xlab = "Date", ylab =

I managed to use col = TEMP3["SITE"] to plot the two different sites( BG1
and EA7) in different colours, but I am struggling to change the colours. 

I wanted to up a colour scheme to match the site, so tried 

BG1 <- "blue"
EA7 <- "green"

before the plot function, but the graphic just came out with red and black
as before. 

There are other datasets in which there are more than two sites so I would
really like to learn how to use colour to distinguish between them on a

Any direction would be very greatly received!

Thank you very much


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