NA

mm <- c(85, NA, 120)
print(is.na(mm))
print(mean(mm, na.rm = TRUE))

mm <- c(Nairobi = 85, Mombasa = NA, Kisumu = 120)
print(mm[!is.na(mm)])

print(sum(c(12, NA, 5), na.rm = TRUE))

print(ifelse(is.na(c(4, NA, 3)), 0, c(4, NA, 3)))