R help - Jun 2008 - using the stepfun to plot histogram outline.

Hello list:)

I have lots of values which I would like to get a histogram outline
out of.

An example of what I am talking about:

testdata = runif(100)
bbb = seq(0,1, by = 0.01)
hist(testdata, breaks = bbb)

I would like to get the outline of the resulting histogram.

Now, I think that I can do this using the stepfun function. However, I
am uncertain of how to get to the data the stepfun function require.
>From ?stepfun
Arguments:

       x: numeric vector giving the knots or jump locations of the step
          function for 'stepfun()'.  For the other functions,
'x' is as
          'object' below.

       y: numeric vector one longer than 'x', giving the heights of the
          function values _between_ the x values.


X I think is the same as bbb above. I am however uncertain of how I
would go about getting the data needed for y, given that the data I
have is on the same format as testdata above is.

Thanks for your help!

Karin
-- 
Karin Lagesen, PhD student
karin.lagesen at medisin.uio.no
http://folk.uio.no/karinlag

On Sat, Jun 21, 2008 at 3:36 AM, Karin Lagesen <karinlag at
studmed.uio.no> wrote:
>
> Hello list:)
>
> I have lots of values which I would like to get a histogram outline
> out of.
>
> An example of what I am talking about:
>
> testdata = runif(100)
> bbb = seq(0,1, by = 0.01)
> hist(testdata, breaks = bbb)
>
> I would like to get the outline of the resulting histogram.
Do you want to draw the outline, or create a function that represents
it? (that's what stepfun will do)  Either way looking at:

h <- hist(testdata, breaks = bbb)
str(h)

will probably be helpful.

Hadley

-- 
http://had.co.nz/

All; this might be an easy question but I cannot make it work. I would
like to set the min and max of the y axis of a plot. I know I have to
use par("usr"), but after I do the plot() the axis values get changed.

x<-rnorm(20)
Y<-x+rnorm(20,0,.1)
plot(y,x)
par("usr")

# let's say I have -2.8 1.15 -2.8 1.16 for par("usr")
# let's say I need to change the Y-axis to be -5 to 5

usr<-par("usr")
par(usr=c(usr[1:2],-5,5))
plot(y,x)

# it does not take the -5 to 5???

Is there any way to set the axis values?

Thanks