How to get the mode of a group in summarize in R

I use this approach:

df <- data.frame(groups = c("A", "A", "A", "B", "B", "C", "C", "C", "D"), nums = c("1", "2", "1", "2", "3", "4", "5", "5", "1"))

which looks like:

 groups nums
  A    1
  A    2
  A    1
  B    2
  B    3
  C    4
  C    5
  C    5
  D    1

Then I define:

mode <- function(codes){
  which.max(tabulate(codes))
}

and do the following:

mds <- df %>%
  group_by(groups) %>%
  summarise(mode = mode(nums))

giving:

  groups  mode
 A          1
 B          2
 C          5
 D          1

You need to make a couple of changes to your code for mlv to work.

1. the method (mfv) has to be within quotes ('mfv'). That is what is causing your error.
2. After you do that, since mlv returns a list, you have to feed one value to summarise(). Assuming that you want the mode ('M'), you pick that element from the list.

Try:

dataSummary <- dataObs %>%
  group_by(ParNonPar, CPTCode) %>%
  summarise(mean = mean(net_paid), 
            meadian=median(net_paid), 
            mode = mlv(net_paid, method='mfv')[['M']], 
            total = sum(net_paid))

to get:

> dataSummary
Source: local data frame [3 x 6]
Groups: ParNonPar

  ParNonPar CPTCode     mean meadian     mode   total
1         N     104 639.7111  893.00 622.7333 5757.40
2         Y     100   0.0000    0.00   0.0000    0.00
3         Y     103 740.2800  740.28 740.2800  740.28

Hope that helps you move forward.