I have 2 series of data a,b and I would like to calculate a new series which is z[t] = z[t-1]*a[t] + b[t] , z[1] = b[1]. How can I do that without using a loop? -- View this message in context: http://r.789695.n4.nabble.com/aplpy-recursive-function-on-a-list-tp4328017p4328017.html Sent from the R help mailing list archive at Nabble.com.