👀 Views: 37 💬 Answers: 1 📅 Created: 2025-06-03

r dplyr dataframe R

I'm testing a new approach and I've been banging my head against this for hours. I'm working with an scenario while trying to apply a custom function to a grouped data frame using `dplyr`. Specifically, I want to calculate the median of a column after grouping by another column, but I keep running into an behavior that says, "behavior in summarise(): Column `median_col` must be length 1 (the result has 3)." Here's the relevant code snippet: ```r library(dplyr) # Sample data frame set.seed(123) data <- data.frame( group = rep(c('A', 'B', 'C'), each = 5), value = rnorm(15) ) # Custom function to calculate median calc_median <- function(x) { return(median(x)) } # Attempting to group by 'group' and summarise result <- data %>% group_by(group) %>% summarise(median_col = calc_median(value), .groups = 'drop') ``` This results in the aforementioned behavior, which I don't understand since I'm expecting a single median value per group. I have tried using base R functions and have also checked that the input to `calc_median` is as expected. Additionally, I've tested the same operation using a different aggregation method like `mean`, and it works fine: ```r result_mean <- data %>% group_by(group) %>% summarise(mean_col = mean(value), .groups = 'drop') ``` Could anyone point out what I might be doing wrong with the `median` calculation? I'm using R version 4.1.0 and `dplyr` version 1.0.7. My development environment is macOS. Any help would be greatly appreciated! I'm working with R in a Docker container on Debian. I'd really appreciate any guidance on this. Any ideas what could be causing this? For reference, this is a production CLI tool. Thanks for any help you can provide!