Writing Functions in R

Examples

Use the `longesttest` function to print the longest name in the `NAME` column of the 1980 election data.

longesttest <- function(x) {x[which.max(nchar(x))]}

Click to see solution

library(data.table)
myDF <- fread("/anvil/projects/tdm/data/election/itcont1980.txt", quote="")
names(myDF) <- c("CMTE_ID", "AMNDT_IND", "RPT_TP", "TRANSACTION_PGI", "IMAGE_NUM", "TRANSACTION_TP", "ENTITY_TP", "NAME", "CITY", "STATE", "ZIP_CODE", "EMPLOYER", "OCCUPATION", "TRANSACTION_DT", "TRANSACTION_AMT", "OTHER_ID", "TRAN_ID", "FILE_NUM", "MEMO_CD", "MEMO_TEXT", "SUB_ID")
longesttest <- function(x) {x[which.max(nchar(x))]}

longesttest(myDF$NAME)

'REPUBLICAN NATIONAL COMMITTEE - CONTRIBUTIONS (AKA REPUBLICAN NATIONAL FINANCE COMMITTEE'

Using the itcont1980.txt file, create your own function called `mostpopulardate` that finds the most popular date in a column of dates, as well as the number of times that date occurs. Use that function to find the most popular transaction date.

Click to see solution

library(data.table)
myDF <- fread("/anvil/projects/tdm/data/election/itcont1980.txt", quote="")
names(myDF) <- c("CMTE_ID", "AMNDT_IND", "RPT_TP", "TRANSACTION_PGI", "IMAGE_NUM", "TRANSACTION_TP", "ENTITY_TP", "NAME", "CITY", "STATE", "ZIP_CODE", "EMPLOYER", "OCCUPATION", "TRANSACTION_DT", "TRANSACTION_AMT", "OTHER_ID", "TRAN_ID", "FILE_NUM", "MEMO_CD", "MEMO_TEXT", "SUB_ID")
mostpopulardate = function(x) {tail(sort(table(x)), n=1)}
mostpopulardate(myDF$TRANSACTION_DT)

x
12311979
    2562

Using the itcont1980.txt file, write a function called myindycities that takes a year as the input and uses tapply to make a table of length 10, containing the top 10 cities in Indiana according to the sum of the amount of donations (in dollars) given in each city.

Click to see solution

myindycities <- function(myyear) {
    myDF <- fread(paste0("/anvil/projects/tdm/data/election/itcont", myyear, ".txt"), quote="", select = c(9, 10,15))
    names(myDF) <- c("city", "state", "donation")
    myDF <- myDF[myDF$state == "IN", ]
    city_donations <- tapply(myDF$donation, myDF$city, sum)
    sorted_cities <- sort(city_donations, decreasing = TRUE)
    return(head(sorted_cities, 10))
}

myindycities(1980)
myindycities(1986)
myindycities(1992)

INDIANAPOLIS
    753547
MUNCIE
    159897
ELKHART
    111385
EVANSVILLE
    94605
FORT WAYNE
    87115
CARMEL
    85872
INDPLS
    76396
FT WAYNE
    70174
SOUTH BEND
    68332
LAFAYETTE
    49851

INDIANAPOLIS
    995379
FORT WAYNE
    149194
MUNCIE
    100433
ELKHART
    100350
EVANSVILLE
    84815
SOUTH BEND
    81841
CARMEL
    75993
TERRE HAUTE
    62361
ZIONSVILLE
    50900
COLUMBUS
    40400

INDIANAPOLIS
    2583618
FORT WAYNE
    524980
CARMEL
    384683
EVANSVILLE
    308566
SOUTH BEND
    274397
MUNCIE
    251164
ELKHART
    196432
COLUMBUS
    143096
BLOOMINGTON
    121733
ZIONSVILLE
    94370