library(dplyr)

How to use piping in R

Normally, you would do this:

head(mtcars)

##                    mpg cyl disp  hp drat    wt  qsec vs am gear carb
## Mazda RX4         21.0   6  160 110 3.90 2.620 16.46  0  1    4    4
## Mazda RX4 Wag     21.0   6  160 110 3.90 2.875 17.02  0  1    4    4
## Datsun 710        22.8   4  108  93 3.85 2.320 18.61  1  1    4    1
## Hornet 4 Drive    21.4   6  258 110 3.08 3.215 19.44  1  0    3    1
## Hornet Sportabout 18.7   8  360 175 3.15 3.440 17.02  0  0    3    2
## Valiant           18.1   6  225 105 2.76 3.460 20.22  1  0    3    1

However, with piping, this would look different:

mtcars %>% head()

##                    mpg cyl disp  hp drat    wt  qsec vs am gear carb
## Mazda RX4         21.0   6  160 110 3.90 2.620 16.46  0  1    4    4
## Mazda RX4 Wag     21.0   6  160 110 3.90 2.875 17.02  0  1    4    4
## Datsun 710        22.8   4  108  93 3.85 2.320 18.61  1  1    4    1
## Hornet 4 Drive    21.4   6  258 110 3.08 3.215 19.44  1  0    3    1
## Hornet Sportabout 18.7   8  360 175 3.15 3.440 17.02  0  0    3    2
## Valiant           18.1   6  225 105 2.76 3.460 20.22  1  0    3    1

You may wonder, what’s the point?

If you need to apply multiple functions on one dataframe, piping saves you a lot of typing, and makes for tidy R code. An example:

mtcars %>% 
  mutate(dec = mpg/10) %>%
  select(mpg, dec, am) %>%
  filter(am == "1")

##     mpg  dec am
## 1  21.0 2.10  1
## 2  21.0 2.10  1
## 3  22.8 2.28  1
## 4  32.4 3.24  1
## 5  30.4 3.04  1
## 6  33.9 3.39  1
## 7  27.3 2.73  1
## 8  26.0 2.60  1
## 9  30.4 3.04  1
## 10 15.8 1.58  1
## 11 19.7 1.97  1
## 12 15.0 1.50  1
## 13 21.4 2.14  1

What did we do:

1. We created a new column ‘dec’ using mutate(). This column ‘dec’ consists of the values of column mpg divided by 10.
2. We selected the columns ‘mpg’, ‘dec’ and ‘am’ using select().
3. We filtered for the value ‘1’ in the column ‘am’ using filter().

And all of this in just one step!

Now what?

We have created a new column, but this column is not part of our dataframe yet! We could do this:

mtcars <- mtcars %>% 
  mutate(dec = mpg/10)

OR… we could do this!

library(magrittr)

mtcars %<>% 
  mutate(dec = mpg/10)

Soooo easy!

This has been our first introduction to piping. There is however much more to learn! That is why you should definitely go to this link.