👀 Views: 47 💬 Answers: 1 📅 Created: 2025-06-13

r purrr dataframes R

I'm getting frustrated with I'm working on a project where I need to apply a function to a list of data frames using `purrr::map`. My goal is to calculate the mean of a specific column in each data frame and return a list of the results. However, I'm working with unexpected `NULL` outputs for some of the data frames, which doesn't seem right. Here’s what I’ve tried so far: I have a list of data frames, `df_list`, each containing a column named `value`. Here's how I set it up: ```r library(purrr) # Sample list of data frames set.seed(123) df1 <- data.frame(value = rnorm(5)) df2 <- data.frame(value = rnorm(5)) df3 <- data.frame(value = NA_real_) # This one has NA df_list <- list(df1, df2, df3) ``` I’m using `map` to calculate the mean: ```r mean_values <- map(df_list, ~ mean(.x$value, na.rm = TRUE)) ``` When I run this code, I get the following output: ```r [[1]] [1] 0.2055754 [[2]] [1] -0.4486178 [[3]] NULL ``` I expected the mean of the third data frame to be `NA` instead of `NULL`. I’ve also tried using `map_dbl` instead of `map`, thinking that might help, but I ended up with the same result. Is there a way to ensure that I get `NA` instead of `NULL` for data frames that contain only `NA` values? Any guidance on how I can modify my approach to achieve this would be greatly appreciated! I've been using R for about a year now. I'd really appreciate any guidance on this. I'm working in a Windows 10 environment. Any help would be greatly appreciated!