data vector to corresonding percentile ranks

I have a problem where I need to calculate the corresponding cohort
percentile ranks for each of several variables.

Essentially, what I need is a function that will calculate the
distribution-free percentiles from each variable's data vector, returning a
corresponding vector of percentiles:

e.g.:

percentile.my.data<-/function/(my.data)


I tried to make ecdf() perform this task but was unsuccessful.

I'd be grateful for any help or advice...