Counting the amount of observations for different factor levels

I am working on a video game dataset and would like a variable column that counts the number of games produced for each platform. I ordered it by year, so ideally it will be a cumulative total over-time for each platform. Here is the function that I tried, but did not work.

counting  <- function(w) {
 i = 0
 j = 0
 k = 0
 l = 0
 m = 0
for (val in w) {
 if(val == "PC"){
  i = i+1
  i
 } else if (val == "Xbox"){
  j = j+1
  j
 }else if (val == "Nintendo"){
  k = k+1
  k
 } else if (val == "Playstation"){
  l = l+1
  l
} else if (val == "Others"){
  m = m+1
  m
 }
 }
}
my_vector2 <- sapply(data$Platform.type, counting)

Does anyone have any suggestions? All I am getting is a really long vector of null.