Selecting Max Column Values in R
r
Solution
You can use `ave` with a custom function that wraps `max`, so you can remove `NA` values:
Data$Y <- ave(Data$Y, Data$X, FUN=function(x) max(x, na.rm=TRUE))
Problem
I'm pretty new to R and have a question regarding selecting the max values in a column. I have the following data frame: ``` X Y [1,] 1 10 [2,] 1 12 [3,] 1 NA [4,] 2 5 [5,] 2 6 [6,] 2 7 [7,] 2 8 [8,] 3 NA [9,] 3 NA [10,] 3 1 ``` I would like to select the max value of column Y and replace all values of Y within each group with that value. My output data frame would look like this: ``` X Y [1,] 1 12 [2,] 1 12 [3,] 1 12 [4,] 2 8 [5,] 2 8 [6,] 2 8 [7,] 2 8 [8,] 3 1 [9,] 3 1 [10,] 3 1 ``` Any help would be appreciated. Thanks! Here's the data ``` Data <- structure(list(X = c(1L, 1L, 1L, 2L, 2L, 2L, 2L, 3L, 3L, 3L), Y = c(10L, 12L, NA, 5L, 6L, 7L, 8L, NA, NA, 1L)), .Names = c("X", "Y"), class = "data.frame", row.names = c("[1,]", "[2,]", "[3,]", "[4,]", "[5,]", "[6,]", "[7,]", "[8,]", "[9,]", "[10,]")) ```