How can I extract numbers from dataframe names in a list in R?

I have a list called list.data with over 600 dataframes in it. Each data frame has a unique name e.g. 4dMU6_20080605tp.txt and within the name is a date "20080605" that I want to extract and add to a new column in each dataframe.

I have created the new column in each dataframe with the column title "Date" but now need to extract the numbers from multiple dataframe names- any idea how I could do this?

I've tried sapply but presumably it doesn't work as it is searching the dataframes as oppossed to the dataframe names.

sapply(list.data, function(x){as.numeric(x[8])})

Any help would be greatly appreciated!

Solution

Using lapply, we can add new Date column to each data frame in the list, using gsub to obtain the date from the name of each list element.

lst_names <- names(list.data)
list.data <- lapply(lst_names, function(x) {
    list.data[[x]]$Date <- gsub("^.*_|[A-Za-z]*\\.\\w+$", "", x)
    return(list.data[[x]])
})
names(list.data) <- lst_names