R help - Feb 2004 - (Novice-) Problem with the plot-function

Hello,
i have written this little function to draw different normal distributions:

n.Plot <- function(x,my,sigma) {
e <- exp(1)
names(x) <- x
f.x <- (1/(sigma*sqrt(2*pi)))*e^(-1*(((x-my)^2)/2*(sigma^2)))
plot(f.x,type="l",xlim=c(-5,5))
return(f.x)
}

if i define x like this:
x <- seq(-5,5,0.01)

Now 
n.Plot(x,0,1) 
DOES draw the correct plot, but the x-axis is labeled from 0 - 1000.
If i give the plot function the xlim=c(-5,5) option, the plot is only drawn 
for the first 5 values of x.
How do i tell plot not to take the indices of x, but the values (or their 
range) of x for labeling the x-axis ?

Felix Eschenburg

I think you meant to do

plot(x, f.x, ...)

BTW, you've re-invented the wheel. See ?dnorm for evaluating the normal pdf.

Best,
Sundar


Felix Eschenburg wrote:
> Hello,
> i have written this little function to draw different normal distributions:
> 
> n.Plot <- function(x,my,sigma) {
> e <- exp(1)
> names(x) <- x
> f.x <- (1/(sigma*sqrt(2*pi)))*e^(-1*(((x-my)^2)/2*(sigma^2)))
> plot(f.x,type="l",xlim=c(-5,5))
> return(f.x)
> }
> 
> if i define x like this:
> x <- seq(-5,5,0.01)
> 
> Now 
> n.Plot(x,0,1) 
> DOES draw the correct plot, but the x-axis is labeled from 0 - 1000.
> If i give the plot function the xlim=c(-5,5) option, the plot is only drawn
> for the first 5 values of x.
> How do i tell plot not to take the indices of x, but the values (or their 
> range) of x for labeling the x-axis ?
> 
> Felix Eschenburg
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html

See ?range. And note that I changed plot to more explicitly show what is
being plotted.
HTH, Andy


#~~~~~~~~~~~~~~~~~~
n.Plot <- function(x,my,sigma) {
e <- exp(1)
names(x) <- x
f.x <- (1/(sigma*sqrt(2*pi)))*e^(-1*(((x-my)^2)/2*(sigma^2)))
plot(x, f.x, type="l", xlim = range(x))
return(f.x)
}

n.Plot(seq(-5,5,0.01),0,1)
n.Plot(seq(-50,50,0.01),0,0.1)

Atropin75 at t-online.de (Felix Eschenburg) writes:
> Hello,
> i have written this little function to draw different normal distributions:
> 
> n.Plot <- function(x,my,sigma) {
> e <- exp(1)
> names(x) <- x
> f.x <- (1/(sigma*sqrt(2*pi)))*e^(-1*(((x-my)^2)/2*(sigma^2)))
> plot(f.x,type="l",xlim=c(-5,5))
> return(f.x)
> }
> 
> if i define x like this:
> x <- seq(-5,5,0.01)
> 
> Now 
> n.Plot(x,0,1) 
> DOES draw the correct plot, but the x-axis is labeled from 0 - 1000.
> If i give the plot function the xlim=c(-5,5) option, the plot is only drawn
> for the first 5 values of x.
> How do i tell plot not to take the indices of x, but the values (or their 
> range) of x for labeling the x-axis ?
Tell plot what your x coordinates are:

plot(x, f.x, type="l", xlim=c(-5,5))
     
-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907

Thank you all, that did the trick. Sometimes i can be a real blockhead.


> Atropin75 at t-online.de (Felix Eschenburg) writes:
> > Hello,
> > i have written this little function to draw different normal
> > distributions:
> >
> > n.Plot <- function(x,my,sigma) {
> > e <- exp(1)
> > names(x) <- x
> > f.x <- (1/(sigma*sqrt(2*pi)))*e^(-1*(((x-my)^2)/2*(sigma^2)))
> > plot(f.x,type="l",xlim=c(-5,5))
> > return(f.x)
> > }
> >
> > if i define x like this:
> > x <- seq(-5,5,0.01)
> >
> > Now
> > n.Plot(x,0,1)
> > DOES draw the correct plot, but the x-axis is labeled from 0 - 1000.
> > If i give the plot function the xlim=c(-5,5) option, the plot is only
> > drawn for the first 5 values of x.
> > How do i tell plot not to take the indices of x, but the values (or
their
> > range) of x for labeling the x-axis ?
>
> Tell plot what your x coordinates are:
>
> plot(x, f.x, type="l", xlim=c(-5,5))

Felix,

there may be more elegant ways of plotting the normal curve, but given your 
current program, you can simply change your plot statment to use a formula:

plot(f.x ~ x, type="l", xlim=c(-5,5))

Dan Nordlund

---------Original message----------
In a message dated 2/5/2004 2:52:04 PM Pacific Standard Time, 
Atropin75 at t-online.de writes:
Hello,
i have written this little function to draw different normal distributions:

n.Plot <- function(x,my,sigma) {
e <- exp(1)
names(x) <- x
f.x <- (1/(sigma*sqrt(2*pi)))*e^(-1*(((x-my)^2)/2*(sigma^2)))
plot(f.x,type="l",xlim=c(-5,5))
return(f.x)
}

if i define x like this:
x <- seq(-5,5,0.01)

Now 
n.Plot(x,0,1) 
DOES draw the correct plot, but the x-axis is labeled from 0 - 1000.
If i give the plot function the xlim=c(-5,5) option, the plot is only drawn 
for the first 5 values of x.
How do i tell plot not to take the indices of x, but the values (or their 
range) of x for labeling the x-axis ?

Felix Eschenburg