5.3: Tidyverse in Action

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To see the tidyverse in action, let’s clean up the NHANES dataset. Each individual in the NHANES dataset has a unique identifier stored in the variable ID. First let’s look at the number of rows in the dataset:

nrow(NHANES)

## [1] 6779

Now let’s see how many unique IDs there are. The unique() function returns a vector containing all of the unique values for a particular variable, and the length() function returns the length of the resulting vector.

length(unique(NHANES$ID))

## [1] 6779

This shows us that while there are 10,000 observations in the data frame, there are only 6779 unique IDs. This means that if we were to use the entire dataset, we would be reusing data from some individuals, which could give us incorrect results. For this reason, we wold like to discard any observations that are duplicated.

Let’s create a new variable called NHANES_unique that will contain only the distinct observations, with no individuals appearing more than once. The dplyr library provides a function called distinct() that will do this for us. You may notice that we didn’t explicitly load the dplyr library above; however, if you look at the messages that appeared when we loaded the tidyverse library, you will see that it loaded dplyr for us. To create the new data frame with unique observations, we will pipe the NHANES data frame into the distinct() function and then save the output to our new variable.

NHANES_unique <- 
  NHANES %>% 
  distinct(ID, .keep_all = TRUE)

If we number of rows in the new data frame, it should be the same as the number of unique IDs (6779):

nrow(NHANES_unique)

## [1] 6779

In the next example you will see the power of pipes come to life, when we start tying together multiple functions into a single operation (or “pipeline”).