[R] Newbie graphing questions
Marc Schwartz
MSchwartz at medanalytics.com
Thu Aug 28 04:36:55 CEST 2003
On Wed, 2003-08-27 at 17:28, Francisco J. Bido wrote:
> Hi everyone. R is new to me and I'm very impressed with its
> capabilities but still cannot figure out how to do some basic things.
> There seems to be no lack of documentation but finding what I need has
> proven difficult. Perhaps you can help.
>
> Here's what I'm after:
>
> 1. How do I create a new plot without erasing the prior one i.e., have
> a new window pop up with the new graph? I'm on MacOSX using the Carbon
> port.
In general, if you want to leave the existing device open and have a new
device open for a new plot, you simply call the device name that you
want to open (ie. under Linux you would use X11() ) to open a new
plotting device on the display. See ?Devices for more details.
> 2. How do I pause between plot renderings i.e., in such a way that it
> will draw the subsequent graph after pressing the space bar (or any
> other key).
Set 'par(ask = TRUE)' before plotting. See ?par
> 3. Illustrating critical regions. Say I wanted to illustrate the
> critical region of a standard normal. I would need to draw a vertical
> line from the critical point to the curve and then shade the critical
> region. How do I do this in R?
# Generate a sequence of x values
x <- seq(-3, 3, by = 0.001)
# Plot normal curve over x
plot(x, dnorm(x), type = "l")
# Define left side boundary using min(x)
# and CritVal using alpha = 0.05
alpha <- 0.05
CritVal <- qnorm(alpha / 2)
x.l <- seq(min(x), CritVal, length = 100)
y.l <- c(dnorm(x.l), 0, 0)
# add CritVal, min(x) to complete polygon
x.l <- c(x.l, CritVal, min(x))
# draw and fill left region
polygon(x.l, y.l, density = 50)
# Do the same for right side boundary using max(x)
# and Crit Val
CritVal <- qnorm(1 - (alpha / 2))
x.r <- seq(CritVal, max(x), length = 100)
y.r <- c(dnorm(x.r), 0, 0)
# add max(x) and CritVal to complete polygon
x.r <- c(x.r, max(x) , CritVal)
# draw and fill left region
polygon(x.r, y.r, density = 50)
HTH,
Marc Schwartz
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