##Fibonacci numbers
##Plot Fibonacci spiral 

library(shape) ## we need it for plotting

## Use install.packages("shape") if your R version does not know the
## shape package

## Function to produce the spiral plot
plot.Fib <- function(x){
    plot(-max(x):max(x),-max(x):max(x),type="n",
         xlab="",ylab="",main="Fibonacchi spiral") #empty plot
    x.coor <- c(0,0,cumsum(x*rep(c(1,0,-1,0),length=length(x)))) #x-coordinate for the center of the circle
    y.coor <- c(0,0,cumsum(x*rep(c(0,1,0,-1),length=length(x)))) #y-coordinate for the center of the circle
    a1 <- 0:length(x)*pi/2 #angle start
    a2 <- 1:(length(x)+1)*p/2 #angle end 
    for ( i in 1:length(x)){
            plotcircle(r=x[i],mid=c(x.coor[i],y.coor[i]),
                       from=a1[i],to=a2[i]) #plot the quartercircles
        }
  }

# Not-so-efficient function to generate Fibonacci numbers
Fibonacci <- function(n) { 
  if (n==NaN) break ##  function can only take numerical values
  if (n==1) {
        x <- 0
    } else {
        x <- c(0,1)
        while (length(x) < n) {
            k <- length(x)
            x[k+1] <- x[k] + x[k-1]
        }
    } #end while loop
  plot.Fib(x)    # finally call the plot function defined above
  return(x)      # and return the full series
}