Using tidyverse, how can you generate new columns dynamically? - r

Question

Say I have a dataframe of tens of columns, and my custom function needs each one of these columns plus a number in a vector to give me the desired output. After being done with all that, I need to generate new column names based on the original column names in the dataframe. How to accomplish this using the tidyverse, instead of for loops or other solutions in base R.
MWE
structure(list(col1 = c(36.0520583373645, 37.9423749063706, 33.6806634587719,
34.031649012457, 29.5448679963449, NA, 34.7576769718877, 30.484217745574,
32.9849083643022, 27.4081694831058, 35.8624919654559, 35.0284347997991,
NA, 32.112605893241, 27.819354948082, 35.6499532124921, 35.0265642403216,
32.4006569441297, 30.3698557864842, 31.8229364456928, 34.3715903109276
), col2 = c(32.9691195198199, 35.6643664156284, 33.8748732989736,
34.5436311813644, 33.2228201914256, 38.7621696867191, 34.8399804318992,
32.9063078995457, 35.7391166214367, 32.7217251282669, 36.3039268989853,
35.9607654868559, 33.1385915196435, 34.7987649028199, 33.7100463668523,
34.7773403671057, 35.8592997980752, 33.8537127786535, 31.9106243803505,
39.3099469314882, 35.1849826815196), col3 = c(33.272278716963,
NA, 31.8594920410129, 33.1695042551974, 29.3800694974438, 35.1504378875245,
34.0771487001433, 29.0162879030415, 30.6960024888799, 29.5542117965184,
34.3726321365982, 36.0602274148362, 33.1207772548047, 31.5506876209822,
28.8649303491974, 33.4598790144265, 30.5573454464747, 31.6026723913051,
30.4716061556625, 33.009463000301, 30.846230953425)), row.names = c(NA,
-21L), class = "data.frame")
save above in a file, and then use example <- dget(file.choose()) to read the above dataframe.
Code
y <- c (2, 1, 1.5)
customfun <- function(x, y){
n <- log (x) * y
print (n)
}
df <- example %>%
dplyr::mutate(col1.log = customfun (col1, y = y[1])) %>%
dplyr::mutate(col2.log = customfun (col2, y = y[2])) %>%
dplyr::mutate(col3.log = customfun (col3, y = y[3]))
Question
Imagine I have tens of these columns not only 3 as in the MWE, how to generate the new ones dynamically using the tidyverse?

Answer 1

We can use map2 and bind_cols to add new columns
library(dplyr)
library(purrr)
bind_cols(example, map2_df(example, y, customfun) %>%
rename_all(~paste0(., ".log")))
# col1 col2 col3 col1.log col2.log col3.log
#1 36.05206 32.96912 33.27228 7.169928 3.495571 5.257087
#2 37.94237 35.66437 NA 7.272137 3.574152 NA
#3 33.68066 33.87487 31.85949 7.033848 3.522674 5.192003
#4 34.03165 34.54363 33.16950 7.054582 3.542223 5.252446
#...

Answer 2

tidyverse is not great for these sweep()-like operations, however, one option could be:
example %>%
do(., sweep(., 2, FUN = customfun, y)) %>%
rename_all(~ paste(., "log", sep = "."))
col1.log col2.log col3.log
1 7.169928 3.495571 5.257087
2 7.272137 3.574152 NA
3 7.033848 3.522674 5.192003
4 7.054582 3.542223 5.252446
5 6.771820 3.503237 5.070475
6 NA 3.657445 5.339456
7 7.096801 3.550766 5.292941
8 6.834418 3.493664 5.051786
9 6.992100 3.576246 5.136199
10 6.621682 3.488039 5.079339