[R] pie chart in lattice - trellis class

[Patrick Giraudoux]

Jim Lemon a écrit :
> Patrick Giraudoux wrote:
>> Dear all,
>>
>> After going through the Lattice doc and R-help list and google, I got 
>> the feeling that there is no function in lattice or other package to 
>> compute a pie chart object  of class "trellis". Although pie charts 
>> are obviously not considered optimal even in the pie() doc ;-) ,  pie 
>> chart trellis objects would be easy positioned e.g. over a map drawn 
>> with the grids package.
>>
>> Can anybody confirm this absence or indicate a package/function able 
>> to draw a pie chart  object of class trellis?
>>
> Hi Patrick,
> Floating.pie was written to solve this problem, but it only works in 
> standard graphics. Perhaps it might help, though.
>
> Jim

Hey ! Looks like exactly the one I was looking for... For info to other 
R-users, it can be found in the 'plotrix' package. Meanwhile I had 
dropped some line codes with the same target, still  not fully achieved 
(the argument center is not taken into account yet... needs one line more).

Thanks a lot!

Patrick


polycirc2<-function (radius=1, center = c(0, 0), edges = 50, init=pi/2, 
angle=pi/2)
{
    circ = NULL
    angles <- seq(init, init+angle, l = edges)
    for (i in angles) {
        circ <- rbind(circ, cbind(radius * sin(i), radius * cos(i)))
    }
    circ<-rbind(c(0,0),circ)
    return(cbind(circ[, 1] + center[1], circ[,2] + center[2]))
}


pie2<-function(x,col=NULL,...){
    x<-x/sum(x)
    xC<-cumsum(x)
    xC<-xC/xC[length(xC)]
    init=0
        for (i in 1:length(x)) {
        angle<-x[i]*2*pi
        polygon(polycirc2(init=init,angle=angle),col=col[i],...)
        init<-xC[i]*2*pi
    }
}

# example
ex<-rpois(10,2)
plot(c(-1,+1),c(-1,+1),type="n",asp=1)
pie2(ex,col=c(1:length(ex)))