caloffset = function(genome){
    total_len = sum(as.numeric(genome[,2]))
    offset = 0
    for (i in 1:nrow(genome)) {
        offset = c(offset,offset[i]+genome[i,2])        
    }
    offset    
}

coverage = function(intervals,genome,offset,resolution) {

    nChr = length(offset) - 1
    total_len = offset[nChr+1]
    nbin = as.integer(total_len / resolution)

	pos = numeric(0)
    cov = numeric(0)#coverage
    col = numeric(0)#color
    for (i in 1:nChr) {
        d = x[x[,1]==as.character(genome[i,1]),2:3]
        d = ceiling(((d[,1]+d[,2])/2+offset[i])*nbin/total_len)
        t = table(d)
		pos = c(pos,as.numeric(row.names(t)))
        cov = c(cov, as.numeric(t))
        col = c(col,numeric(length(t))+i)
    }
    list(nbin=nbin,pos=pos,cov=cov,col=col)
}

# plot coverage
# res = genomeView(x,genome,100000)
plotcov = function(res,genome,offset,title,uselog) {
	if (uselog == 'log'){
		res$cov = log10(res$cov+1)
	}
    ymax = max(res$cov)
	par(mar=c(5,5,5,1))
    plot(res$pos,res$cov,type='h',cex=0.1,cex.axis=2,cex.lab=2,cex.main=3,col=res$col,xaxt='n',main=title,xlab='chromosome',ylab='coverage',frame.plot=F,xlim=c(0,res$nbin),ylim=c(0,ymax))
    xticks = numeric(nrow(genome))
    for (i in 1:nrow(genome)){
       xticks[i] = (offset[i]+offset[i+1])/2*res$nbin/offset[length(offset)]
    }
    mtext(genome[,1],side=1,at=xticks,adj=1,las=2,col=seq(nrow(genome)))
}