How to break data in quantiles properly?

Hi,

I would like to break a dataset in n.classes quantiles.
Till now, I used the following code:
Classify.Quantile <- function (dataset, nclasses = 10) 
{
	n.probs <- seq(0,1,length=nclasses+1)
	n.labels = paste("C", 1:nclasses-1, sep="")
	n.rows <- nrow(dataset)
	n.cols <- ncol(dataset)
	n.motif <- dataset
	
	for (j in 2:n.cols)
	{
		cat(j, "  ");
		discr = n.labels[unclass(cut(dataset[,j],quantile(dataset[,j],n.probs),include.lowest=T))]
		n.motif[,j] = discr
	}
	
	res <- list(motif=n.motif, labels=n.labels, n.classes=nclasses)
	return(res)
}


but if you try to call this with a dataset with a lot of same value, you got a 
Error in cut.default(dataset[, j], quantile(dataset[, j], n.probs),
include.lowest = T) :
        cut: breaks are not unique

I perfectly understand why but I would like to know how to avoid this behaviour.

for e.g., use this code to raise the error:
x=matrix(0,1000,1)
x[100]=1
Classify.Quantile(x, 10)

of course this dataset is a bit extreme but it happens to get data
with very small variance.


Thanks for any help you could provide