How to find the statistical mode of each ID - r

Question

Here are the observations of two individuals of my dataset.
data=structure(list(id = c(2L, 2L, 2L, 3L, 3L, 3L), trt = c(1L, 1L,
1L, 1L, 1L, 1L), status = c(0L, 0L, 0L, 2L, 2L, 2L), stage = c(3L,
3L, 3L, 4L, 4L, 4L), spiders = c(1L, 1L, 1L, 0L, 1L, 0L), sex = structure(c(2L,
2L, 2L, 1L, 1L, 1L), .Label = c("m", "f"), class = "factor"),
hepato = c(1L, 1L, 1L, 0L, 1L, 0L), edema = c(0, 0, 0, 0.5,
0, 0.5), ascites = c(0L, 0L, 0L, 0L, 0L, 0L)), row.names = c(NA,
-6L), class = "data.frame")
I want to calculate the the statistical mode for each individual after grouping by id. I used this code below:
library(dplyr)
library(modeest)
data%>%
group_by(id)%>%mutate(edema2=mlv(edema))
And I get an error message when calculating the mode, while this method work well with other statistical parameters such as mean, sd, min, max....

Answer 1

The warnings that you are getting are suggesting two things.
You have not specified what method to choose so default method 'shorth' is used.
It is suggesting that there is a tie in selection of Mode value.
Alternatively, why not use the Mode function from here :
Mode <- function(x) {
ux <- unique(x)
ux[which.max(tabulate(match(x, ux)))]
}
To apply by group you can use it with dplyr as :
library(dplyr)
data%>% group_by(id)%>% mutate(edema2= Mode(edema))
# id trt status stage spiders sex hepato edema ascites edema2
# <int> <int> <int> <int> <int> <fct> <int> <dbl> <int> <dbl>
#1 2 1 0 3 1 f 1 0 0 0
#2 2 1 0 3 1 f 1 0 0 0
#3 2 1 0 3 1 f 1 0 0 0
#4 3 1 2 4 0 m 0 0.5 0 0.5
#5 3 1 2 4 1 m 1 0 0 0.5
#6 3 1 2 4 0 m 0 0.5 0 0.5