CODEWITHSUNDEEP
rdplyr
Jan Janiszewski
Jan Janiszewski

Reputation: 442

Make rowwise operations on a vector of columns

I would like to understand how I can get the row-wise minimum for a set of columns that are defined in a vector of strings, i.e. how to get the following output with the following input:

Input: 

t <- data.frame(x= c(1,2,3,4), y= c(2,3,4,5), z = c(4,5,6,7))
vars. <- c('x', 'y')

My (not working) suggestion:

t %>% rowwise %>% mutate(min_x_y = min(vars(vars.)))

Output should be:

  x y z min_x_y
1 1 2 4       1
2 2 3 5       2
3 3 4 6       3
4 4 5 7       4

Upvotes: 0

Views: 285

Answers (3)

hendrikvanb
hendrikvanb

Reputation: 459

Yet another alternative to the approaches already suggested would be to use a combination of tidy evaluation and pmin:

# convert character vector of variable names into symbols
vars. <- c('x', 'y') %>% dplyr::syms()

# use tidy evaluation to pass symbols to pmin inside a mutate call
t %>% 
  mutate(min_x_y = pmin(!!!vars.))
#>   x y z min_x_y
#> 1 1 2 4       1
#> 2 2 3 5       2
#> 3 3 4 6       3
#> 4 4 5 7       4

Upvotes: 2

Ronak Shah
Ronak Shah

Reputation: 388807

We can use pmap_dbl from purrr.

library(dplyr)
library(purrr)

t %>% mutate(min_x_y = pmap_dbl(select(., vars.), min))

#  x y z min_x_y
#1 1 2 4       1
#2 2 3 5       2
#3 3 4 6       3
#4 4 5 7       4

A base R version would be

t$min_x_y <- do.call(pmin, t[vars.])

Upvotes: 3

statistic
statistic

Reputation: 181

You can do that in different ways, one is;

t <- data.frame(x= c(1,2,3,4), y= c(2,3,4,5), z = c(4,5,6,7))
vars. <- c('x', 'y')

t$min_x_Y=t(as.data.frame(t(t)) %>%
  summarise_all(funs(min)))

Upvotes: 0

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