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

[David Winsemius]

On Nov 21, 2011, at 2:17 PM, SarahH wrote:

> 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
> archive.
>
> 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 =
> "Temberature[C]")
>
> 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

Instead try

num.site <- as.numeric(TEMP3[,"SITE"])
plot ( x = TEMP3[,"TIME"], y = TEMP3[,"TEMP"], type = "p", col =
num.site, pch = 3, main = "Temperature changes", xlab = "Date", ylab =
"Temberature[C]")

Would create a vector of integer values that are specific to the sites  
and then offere that as argument to col=


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

That would only have created two new objects by that name (unless of  
course you were following someone's misguided directions to use  
attach().)
>
> 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
> plot.
>
> Any direction would be very greatly received!
>
> Thank you very much
>
> Sarah
>
>
>
>
>
> --
> View this message in context: http://r.789695.n4.nabble.com/Scatter-plot-using-colour-to-group-points-tp4092794p4092794.html
> Sent from the R help mailing list archive at Nabble.com.
>
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David Winsemius, MD
West Hartford, CT