cbind specific columns in list (without dplyr package)

Question

I have a list with approximately 50 (slots) - dataframes. Each and every element of this list (dataframe) has 10 columns, 3 of which correspond to "year", "month" and "day". How can I cbind those three columns into one (by creating new column), in every dataframe of this list, and convert them at the same time to as.Date format without using the dplyr package .

I'm sending a reproducible example:

city_A <- data.frame(year = c(1995,1996,1997),month = c(5,6,9),day = c(1,5,8),ozone = c(0.5,0.9,0.12))
city_D <- data.frame(year = c(1982,1959,1909),month = c(3,10,12),day = c(21,24,30),ozone = c(1.5,2.9,3.14))

town_list <- list(city_A,city_D)

The expected outcome is something like this:

[[1]]
  date              year   month day  ozone
1 1995-05-01        1995     5     1    0.5
2 1996-06-05        1996     6     5    0.9
3 1997-09-08        1997     9     8    0.12

[[2]]
  date              year   month day  ozone
1 1982-03-21        1982     3    21    1.5
2 1959-10-24        1959    10    24    2.9
3 1909-12-30        1909    12    30    3.14

score 3 · Answer 1 · answered Feb 03 '22 at 17:44

Use do.call(rbind, x)

city_A <- data.frame(year = c(1995,1996,1997),month = c(5,6,9),day = c(1,5,8),ozone = c(0.5,0.9,0.12))
city_D <- data.frame(year = c(1982,1959,1909),month = c(3,10,12),day = c(21,24,30),ozone = c(1.5,2.9,3.14))

town_list <- list(city_A,city_D)

do.call(rbind, town_list)
#>   year month day ozone
#> 1 1995     5   1  0.50
#> 2 1996     6   5  0.90
#> 3 1997     9   8  0.12
#> 4 1982     3  21  1.50
#> 5 1959    10  24  2.90
#> 6 1909    12  30  3.14

^{Created on 2022-02-03 by the reprex package (v2.0.1)}

score 3 · Accepted Answer · answered Feb 03 '22 at 18:10

We can use ISOdate to transform to create the Date class

lapply(town_list, transform, date = as.Date(ISOdate(year, month, day)))

If it needs to be the first column, either cbind or use column indexing afterwards

lapply(town_list, \(x) 
    cbind(date = with(x, as.Date(ISOdate(year, month, day))), x))

cbind specific columns in list (without dplyr package)

2 Answers2