f1 <- function(x) {
  c(s = sum(x),
    m = mean(x),
    v = var(x))
}

f2 <- function(x) {
  apply(x, 1, f1)
}

for (i in 1:6) {
  assign(paste('var', i, sep = '_'),
runif(30, 20, 100))
}

data_1 <- do.call(
  cbind.data.frame,
  mget(ls(pattern = '*v'))
)

data_1 %>%
  mutate_at(.vars = vars (starts_with('v')),
            .funs = funs(.= f2))

data_1 %>%
  mutate_if(is.numeric, .funs = funs(.= f2))