[R] Extracting data subset for plot
Gavin Simpson
gavin.simpson at ucl.ac.uk
Tue Oct 12 09:10:50 CEST 2010
On Tue, 2010-10-12 at 11:44 +0800, elaine kuo wrote:
> Dear list,
> I want to make a plot based on the following information, using the command
> plot.
>
> variable A for x axis : temperature (range: -20 degrees to 40 degree)
>
> variable B for y axis : altitude (range: 50 m to 2500 m )
Use the subset argument of plot():
## dummy data
dat <- data.frame(temperature = seq(-20, 40, by = 1),
altitude = seq(50, 2500, length = 61))
## use subset to select out the data we want
plot(altitude ~ temperature, data = dat, subset = temperature >= 0)
To understand what this is doing, consider:
with(dat, temperature >= 0)
So temperature >= 0 is yielding a logical vector indicating which rows
of dat are used to form the plot.
If you need to permanently subset your data, there is a subset function
that works the same way:
subset(dat, subset = temperature >= 0)
but yields a data frame of the rows of dat that matched the temperature
condition.
HTH
G
> The data below 0 degree of X variable wants to be erased tentatively.
>
> Please kindly advise the command to extract the data ranging from 0 degree
> to 40 degrees.
>
> Thank you.
>
>
>
> Elaine
>
> [[alternative HTML version deleted]]
>
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