DrawDensity = function(x,bw=5)
{
   if(any(bw<=0))
   {
     bw <- 5

   }
   #print(bw)
   n <- length(x)
   if(any(n>0))
   {
     mn <- min(x)
     mx <- max(x)
     rmn <- (mn %/% bw)
     begx <-  rmn * bw
     rmn <- (mx %/% bw)
     endx <- (rmn) * bw
     if ((mx-rmn * bw) > 0)
     {
        endx <- (rmn+1) * bw
     }

     segs <- (endx-begx)  %/% bw
     segcounts <- numeric(segs)
     validsegs <- 0
     print(segs)
     for(i in 1:segs)
     {
        slw <- begx+(i-1) * bw
        sup <- begx+(i) * bw
        tmp<- x[x > slw & x<=sup];
        segcounts[i]<- length(tmp)
        if(length(tmp)>0)
        {
           validsegs <- validsegs+1
        }
     }
     #计算基本密度:向量长度与图形分割宽度的积倒数.
     baseIndesity = 1 / (n*bw);
     ymax = baseIndesity * (max(segcounts)+1)
     plot(c(begx,endx),c(0,0),xlim=c(begx,endx),ylim=c(0,ymax))
     lines(c(begx,endx),c(0,0))
     lines(c(0,0),c(0,ymax))
     #print(segs)
     for (i in 1:segs)
     {
       x1 <- begx+(i-1) * bw
       x2 <- begx+(i) * bw
       y<- baseIndesity  * segcounts[i]
       drawHist(x1,x2,y)
       #print(i)
     }

   }
}
drawHist = function(x1,x2,y)
{
  #print(x1);print(x2);print(y)
  lines(c(x1,x1),c(0,y))
  lines(c(x1,x2),c(y,y))
  lines(c(x2,x2),c(0,y))
}