[R] loop through columns in a data frame

[jim holtman]

R Notebook

You forgot to provide what your test data looks like. For example, are all
the columns a single letter followed by “_" as the name, or are there
longer names? Are there always matched pairs (‘le’ and ‘me’) or can singles
occur?
Hide

library(tidyverse)# create some data
test <- tibble(a_le = sample(3, 10, TRUE),
               a_me = sample(3, 10, TRUE),
               b_le = sample(3, 10, TRUE),
               b_me = sample(3, 10, TRUE),
               long_le = sample(3, 10, TRUE),
               long_me = sample(3, 10, TRUE),
               short_le = sample(3, 10, TRUE)
)

So get the names of the columns that contain ‘le’ or ‘me’ and group them
together for processing
Hide

col_names <- grep("_(le|me)$", names(test), value = TRUE)
group <- tibble(id = str_remove(col_names, "_.*"), col = col_names)
result <- group %>%
  group_by(id) %>%
  do(tibble(x = rowSums(test[, .$col] == 1)))# add new columns backfor
(i in split(result, result$id)){
  test[, paste0(i$id[1], "_new")] <- as.integer(i$x > 0)
}
test

a_le
<int>
a_me
<int>
b_le
<int>
b_me
<int>
long_le
<int>
long_me
<int>
short_le
<int>
a_new
<int>
b_new
<int>
long_new
<int>
3 1 2 3 1 2 2 1 0 1
2 3 3 2 1 1 1 0 0 1
3 2 3 2 1 3 3 0 0 1
2 3 1 3 3 1 2 0 1 1
1 1 2 1 1 2 2 1 1 1
3 3 3 1 1 1 1 0 1 1
1 2 1 2 2 2 2 1 1 0
1 3 2 3 1 1 3 1 0 1
3 1 1 1 3 3 2 1 1 0
1 1 1 2 3 3 3 1 1 0
1-10 of 10 rows | 1-10 of 11 columns

Jim Holtman
*Data Munger Guru*


*What is the problem that you are trying to solve?Tell me what you want to
do, not how you want to do it.*


On Mon, Mar 25, 2019 at 10:08 AM Yuan, Keming (CDC/DDNID/NCIPC/DVP) via
R-help <r-help using r-project.org> wrote:

> Hi All,
>
> I have a data frame with variable names like A_le, A_me, B_le, B_me, C_le,
> C_me....
> if A_le=1 or A_me=1 then  I need to create a new column A_new=1. Same
> operation to create columns B_new, C_new...
> Does anyone know how to use loop (or other methods) to create new columns?
> In SAS, I can use array to get it done. But I don't know how to do it in R.
>
> Thanks,
>
> Keming Yuan
> CDC
>
>
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>
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