CODEWITHSUNDEEP
rlistfilterdplyrlapply
John Huang
John Huang

Reputation: 845

Filtering by year in a Large List of dataframes

I have a large list of dataframes, and I would like to filter the list in the dataframe by a specific year.

DateAndTime is a column that contains Y-M-D H:M:S, and I would like to filter the list of dataframes by only the year.

plot_list %>% lapply(dplyr::filter(plot_list, format(DateAndTime, "%Y") == year))

I have tried to use lapply on the list, but it doesn't appear to be working. Any help would be appreciated. Thank you.

Upvotes: 1

Views: 378

Answers (1)

akrun
akrun

Reputation: 887098

If we are looping over plot_list, we don't need the plot_list again on filter. In base R, this can be done using subset

plot_list_sub <- lapply(plot_list, subset,
           subset = format(DateAndTime, "%Y") == year)

Or using lambda/anonymous function

plot_list_sub <- lapply(plot_list, function(x) 
        subset(x, format(DateAndTime, "%Y") == year))

Or if we want tidyverse, loop over the list with map (from purrr) and use filter on the list element. Here, we use a lambda function (~) with .x being the element in that list

library(dplyr)
library(purrr)
plot_list_sub <- map(plot_list, ~ .x %>%
                      filter(format(DateAndTime, "%Y") == year))

Upvotes: 3

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