Scatter plot - using colour to group points?

I don't think you can do different colors for a single line (not an
ifelse thing, just a what would that mean sort of thing), but a plot
type like "b" "o" or "h" will work the same way.

Michael

On Mon, Nov 21, 2011 at 4:23 PM, SarahH <sarah.g10 at hotmail.co.uk>  
wrote:

I got the colour vector with ifelse to work, great! Thank you.

Is it possible to use the ifelse colour vector with other plot  
types? For
example with type=l ? I tried but the graphic came back with blue  
lines for
both sites and also a straight line connecting the start and end  
point of
the data?

Thanks
Sarah






Michael Weylandt wrote

I think the easiest way to do this is to set up a color vector with
ifelse and hand that off to the plot command: something like

col = ifelse(TEMP3[,"SITE"] == "BG1", "blue", "green") # Syntax is
ifelse(TEST, OUT_IF_TRUE, OUT_IF_FALSE)

For more complicated schemes, a set of nested ifelse()'s can get you
what you need. There are some other tricks with factors as well, but
they require a little more advanced use of R. Just for the record,
they'd look something like this:

X = letters[c(1,2,3,3,1,2,1,3,3,1,2,2,1)]

colX = c("red","green","blue")[as.factor(X)]

Hope this helps,
Michael

On Mon, Nov 21, 2011 at 2:17 PM, SarahH <sarah.g10 at .co> 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

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
plot.

Any direction would be very greatly received!

Thank you very much

Sarah





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