Function

Write a function called 'rankall' that takes two arguments: an outcome name and a hospital ranking (num). The function reads the outcome-of-care-measures.csv file and returns a 2-column data frame containing the hospital in each state that has the ranking specified in num. The function should return a value
for every state (some may be NA). The first column in the data frame is named hospital, which contains the hospital name, and the second column is named state, which contains the 2-character abbreviation for the state name. Hospitals that do not have data on a particular outcome should be excluded from the set of
hospitals when deciding the rankings. The 'rankall' function should handle ties in the 30-day mortality rates in the same way
that the 'rankhospital' function handles ties. For the purpose of this part of the assignment (and for efficiency), your function should NOT call the 'rankhospital' function from the previous section. The function should check the validity of its arguments. If an invalid outcome value is passed to 'rankall', the function should throw an error via the stop function with the exact message “invalid outcome”. The num variable can take values “best”, “worst”, or an integer indicating the ranking. If the number given by num is larger than the number of hospitals in that state, then the function should return NA.