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

SarahH sarah.g10 at hotmail.co.uk
Mon Nov 21 22:23:13 CET 2011

```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
>>
>>
>>
>>
>>
>> --
>> 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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