How to create a new variable conditioning on another variable in R?

Asked Jan 12 '23 at 18:46

Active Jan 12 '23 at 18:46

Viewed 26 times

Consider the following data:

df <- data.frame(id=c(1,2,3,4,5),
                 v1=c(2020,2020,2021,2021,2022),
                 v2=c(12,5,66,17,17))

I need the output of the form (just averaging v2 based on v1):

id  v1     v2   avg_by_yr
 1  2020   12    8.5
 2  2020    5    8.5
 3  2021   66    41.5
 4  2021   17    41.5
 5  2022   17     17

Thanks!

asked Jan 12 '23 at 18:46

iGada

With `dplyr`, `df %>% group_by(v1) %>% mutate(avg_by_yr = mean(v2))` – Darren Tsai Jan 12 '23 at 18:49
2

Using `base`, `within(df, avg_by_yr <- ave(v2, v1))` – Darren Tsai Jan 12 '23 at 18:51
@DarrenTsai Thanks. Although the second works, the first gives me a different output. – iGada Jan 12 '23 at 18:54
What do you mean about the different output? – Darren Tsai Jan 12 '23 at 18:57
The value of the newly created variable is constant (which is 23.4 on my pc). – iGada Jan 12 '23 at 18:58
1

I guess there is a conflict of packages because you load `plyr` after `dplyr`. You can fix it by specifying the package name, i.e. `df %>% group_by(v1) %>% dplyr::mutate(avg_by_yr = mean(v2))` – Darren Tsai Jan 12 '23 at 19:01
You're right. I loaded the two packages at the same time. Now fixed. Thanks a lot! – iGada Jan 12 '23 at 19:02

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