[R] Constructing variables conditional on two indicators

Dear R users I have a data frame that looks like this: m j X1 X2 1 1 1 2 1 ... 1 J 2 1 2 2 2 ... 2 J . . . M 1 M 2 M ... M J The data frame essentially looks like a

[R] (no subject)

Dear R users I have the following problem when calling optim() to minimize a function "f.obj" (= outer loop) that calls another function "f.con" (a contraction mapping, = inner loop). It seems to me that it is a numerical problem that I currently fail to take into account when coding. Calling