best.R

best <- function(state, outcome) {
    ## Read outcome data
    df <- read.csv("outcome-of-care-measures.csv", colClasses = "character")
    
    ## Check that state and outcome are valid
    ## 'state' is 2-char state code
    ## 'outcome' can be one of “heart attack”, “heart failure”, or “pneumonia”
    by.state <- subset(df, df$State == state)
    if(nrow(by.state) == 0)
        stop("invalid state")
    
    if(outcome == "heart attack")
        col.idx <- 11
    else if(outcome == "heart failure")
        col.idx <- 17
    else if(outcome == "pneumonia")
        col.idx <- 23
    else
        stop("invalid outcome")
    
    ## Return hospital name in that state with lowest 30-day death
    ## rate
    by.state[,col.idx] <- suppressWarnings(as.numeric(by.state[,col.idx]))
    by.cond <- subset(by.state, !is.na(by.state[,col.idx])) #Subset where no cond data
    by.cond <- by.cond[order(by.cond[,col.idx], by.cond$Hospital.Name), ] #Sort by condition, then hospital
    head(by.cond$Hospital.Name, 1)
}