It is my impression that good R programmers make very little use of the for statement. Please consider the following R statement: for( i in 1:(len-1) ) s[i] = log(c1[i+1]/c1[i], base = exp(1) ) One problem I have found with this statement is that s must exist before the statement is run. Can it be written without using a for loop? Would that be better? Thanks, Bob