sum_first_last <- function (vec) vec[1] + vec[length(vec)] midvalue <- function (vec) { if (length(vec) %% 2 == 0) (vec[length(vec)/2] + vec[1+length(vec)/2]) / 2 else vec[(1+length(vec))/2] } sum_positive <- function (vec) { s <- 0 for (e in vec) if (e > 0) s <- s + e s } swap_first_last <- function (vec) { len <- length(vec) result <- vec result[1] <- vec[len] result[len] <- vec[1] result } find_cos_integer <- function (x) { i <- 0 while (abs(cos(i)-x) >= 0.001) i <- i + 1 i } count_char <- function (str, chr) { counts <- numeric(length(str)) for (i in 1:length(str)) { counts[i] <- 0 for (j in 1:nchar(str[i])) if (substring(str[i],j,j) == chr) counts[i] <- counts[i] + 1 } counts }