On 11/07/2012 03:44 AM, Pauli wrote:
Hello,
I am a R beginner and I have a question about a litte function I found.
Here is the code:
# Gambler's Ruin Problem.
# seed capital: k
# rounds: n
# probability of success: p
# number of trials: N
# graphical output (yes/no): draw
# Wait for new graphic (yes/no): ask
ruin<- function( N = 1, n = 10, k = 1, p = 1 / 2,
draw = FALSE, ask = FALSE ){
if(draw)
par( ask = ask )
r<- 0
for( i in 1:N ){
x<- k + cumsum (sample( c(-1, 1),replace = TRUE, n,prob = c(1-p, p)))
if( min(x)<= 0 ){
r<- r + 1
if(draw)
ruin.plot( k, x, col = "red",main = paste(i, "th trial: ruin!" ) )
}
else if(draw)
ruin.plot( k, x, main = paste( i, "th trial: no ruin" ),ylim =
c( 0, max(x) ) )
}
return(r / N)
}
Now I want to start it with for example
"ruin(N=100,n=1000,k=50,draw=TRUE,ask=TRUE)" but i received the message,
that there is an unused argument: (col = "red",main = paste(i, "th trial:
ruin!" ) ).
What is wrong with the code?
Hi Pauli,
Since you received the "unused argument" error message, you may have
defined the "ruin.plot" function somewhere without the "col=" argument.
I tried changing the call to "ruin.plot" to simply "plot", but your k
and x values are of different lengths, so they won't plot anyway. I
think what you may be trying to achieve is more like this:
ruin<-function( N = 1, n = 10, k = 1, p = 1 / 2,
draw = FALSE, ask = FALSE ){
if(draw) par( ask = ask )
r <- 0
plot(0,xlim=c(0,N),ylim=c(-20,k),type="n",main="Gambler's Ruin plot")
for( i in 1:N ){
x <- k + cumsum (sample( c(-1, 1),replace = TRUE, n,prob = c(1-p, p)))
if( min(x) <= 0 ) {
r <- r + 1
if(draw) {
points(i, x[which.min(x)], col = "red" )
text(i,x[which.min(x)]-2,"ruin!")
}
}
else if(draw) points(i, x[which.min(x)], col="green")
}
return(r / N)
}
ruin(N=100,n=1000,k=50,draw=TRUE,ask=TRUE)
Jim
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