1. Write a function that will take a vector as input and return the vector with NAs changed to a null string ('') if the vector is a character vector or to o if it is a numeric vector. Test your function on extreme examples. 3. Extend the previous function so the value to which that NAs are changed can be supplied as a parameter with default value the same as in the previous question. Make the value to which NAs are changed potentially depend on the type of variable. Test your function on extreme examples. 1. Write a function that will take a vector as input and return the vector with NAs changed to a null string ('') if the vector is a character vector or to o if it is a numeric vector. Test your function on extreme examples. 3. Extend the previous function so the value to which that NAs are changed can be supplied as a parameter with default value the same as in the previous question. Make the value to which NAs are changed potentially depend on the type of variable. Test your function on extreme examples