[R] Extracting data subset for plot

[Gavin Simpson]

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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