lists_to_df.r

# Dummy list
z <- list(list('a' = 1, 'b' = 2, 'c' = 3), list('a' = 4, 'b' = 5, 'c' = 6))


# If you just want to stack all of the values, not keeping any of the list name data
# but ensuring they're all of one type
data.frame(values = as.numeric(unlist(z)))



# ldply() automatically keeps the list element names as a ".id" column
z_named <- list('group1' = list('a' = 1, 'b' = 2, 'c' = 3), 'group2' = list('a' = 4, 'b' = 5, 'c' = 6))

# Iterate over the list of *names*
ldply(z_named, .fun = function(x) {

    # Convert to a data.frame that preserves the list name
    data.frame(value = as.numeric(unlist(x)))
    
})