← SASnRArrays-repeat same logic on multiple variables

Introduction

A common chore: apply the same transformation to several columns at once — strip a character from every raw date field, convert every numeric column to a character, replace a sentinel value across multiple columns.
Writing the logic once and looping it over a list of columns keeps the code short and easy to extend when new columns arrive.
SAS expresses this with the ARRAY statement inside a DATA step, plus a DO loop indexed by dim().
Tidyverse uses across() inside mutate(), paired with a tidyselect helper like where() or an explicit column list.
Base R uses lapply() over a column vector, assigning the result back to the same columns of the data frame.
This lesson replaces forward slashes with spaces across three raw date columns on an enrollment dataset.

Arrays-repeat same logic on multiple variables

SAS (Base SAS)+

data ENRLMENT;
 infile datalines dlm='|' dsd missover;
input STUDY : $6. PT : $4. ICDT_RAW : $11. ENRLDT_RAW : $11. RANDDT_RAW : $11.;
label STUDY ='Study Number' PT ='Subject Identifier' ICDT_RAW ='Informed Consent Date' ENRLDT_RAW ='Enrollment Date' RANDDT_RAW ='Randomization Date';
format ;
 datalines4;
CSG001|1001|1/JAN/2010||
CSG001|1002|1/JAN/2010|4/JAN/2010|
CSG001|1003|1/JAN/2010|3/JAN/2010|3/JAN/2010
CSG001|1004|1/JAN/2010|4/JAN/2010|5/JAN/2010
CSG001|1005|15/JAN/2010|1/FEB/2010|5/FEB/2010
CSG001|1006|18/FEB/2010|1/MAR/2010|1/MAR/2010
CSG001|1007|4/APR/2010|14/APR/2010|14/APR/2010
CSG001|1008|20/JUN/2010|26/JUN/2010|27/JUN/2010
;;;;
 run;

data enrl01;
     set enrlment;
     array rvars[*] icdt_raw enrldt_raw randdt_raw;
     do i=1 to dim(rvars);
         rvars[i]=translate(rvars[i],' ','/');
     end;
run;

In SAS, the ARRAY statement lets us name a list of variables once and then refer to them by an index inside a DO loop.
array rvars[*] icdt_raw enrldt_raw randdt_raw; creates an array named rvars that points at the three raw date columns; [*] tells SAS to size the array from the variable list.
do i = 1 to dim(rvars); loops from 1 to the number of elements in the array — dim(rvars) is more robust than hard-coding 3.
rvars[i] = translate(rvars[i], ' ', '/'); runs the TRANSLATE function on the i-th column — replacing / with a space.
The array members are aliases for the real columns, so assigning back through the array updates the underlying variables in the output dataset.
After running, ENRL01 has the same columns as ENRLMENT, with every / in the raw date columns replaced by a space.
Extending the logic to more columns is a one-line edit — add names to the ARRAY statement and the loop keeps working.

R (tidyverse)+

library(tidyverse)
library(stringr)
library(purrr)

enrlment<-tribble(
~study,~pt,~icdt_raw,~enrldt_raw,~randdt_raw,
"CSG001","1001","1/JAN/2010","","",
"CSG001","1002","1/JAN/2010","4/JAN/2010","",
"CSG001","1003","1/JAN/2010","3/JAN/2010","3/JAN/2010",
"CSG001","1004","1/JAN/2010","4/JAN/2010","5/JAN/2010",
"CSG001","1005","15/JAN/2010","1/FEB/2010","5/FEB/2010",
"CSG001","1006","18/FEB/2010","1/MAR/2010","1/MAR/2010",
"CSG001","1007","4/APR/2010","14/APR/2010","14/APR/2010",
"CSG001","1008","20/JUN/2010","26/JUN/2010","27/JUN/2010",
)

enrl01<-enrlment %>% 
  mutate(across(c(icdt_raw, enrldt_raw, randdt_raw), ~ str_replace_all(., "/", " ")))

In tidyverse, across() inside mutate() applies the same function to several columns at once — the direct counterpart of a SAS ARRAY + DO loop.
across(c(icdt_raw, enrldt_raw, randdt_raw), ~ str_replace_all(., "/", " ")) selects the three raw date columns and runs the same str_replace_all() call on each.
The ~ introduces an anonymous function; the . placeholder stands for the current column.
Tidyselect helpers like where(is.character), starts_with("dt_"), or matches("raw$") make it easy to select columns by pattern instead of listing them one by one.
str_replace_all() is from stringr; it replaces every occurrence of the pattern in each value — perfect for turning every / into a space.
We run and confirm ENRL01 has the forward slashes replaced across the three raw-date columns; other columns should be unchanged.

Happy learning!

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Introduction

Arrays-repeat same logic on multiple variables