jim holtman wrote: > try this: > >> b <- c(1, 0, 1, 0, 1, 0, 1, 0, 1, 0) >> p <- c(1, 3, 5, 7) >> b[p] <- ifelse(b[p] == 0, 1, 0) I'll have to look up the ifelse operator, looks like the ternary operator used in C b[p] = b[p]==0?1:0 Cool - thanks! Esmail