Create New Variables

There are endless reasons why you may need to create a new variable. Some examples are:

• Create an ID variable
• Create an indicator variable based on one or more existing variables in your data
  • Ex: control/treatment or at-risk/not at-risk
• Calculate a rowwise summary score
• Recoding or collapsing categories of existing variables into a new variable

The most common function for creating new (and updating existing) variables in a tidyverse fashion is dplyr::mutate(). You will see examples of this function being used throughout almost all scenarios in this resource. Almost any time you recode, create, change class, etc., you will be using the dplyr::mutate() function. Although there are a few other ways I will demonstrate to add columns.

Create a randomly generated column

• Add a random ID variable (See Randomize)

Create a calculated column

• Calculate an age variable
• [Calculate a row sum or mean score](See Calculate Row Values)

Recode existing variables into indicator columns

• Create a correct/incorrect score variable
• Create multiple correct/incorrect score variables
• Create dummy coded variables from a single variable
• Create a preassigned treatment variable
• Create an at-risk indicator variable
• [Create a completion indicator variable](See Select Variables)

Create a constant value column

• Create a constant value variable

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Main functions used in examples

Package	Functions
dplyr	mutate()
tidyr	pivot_wider()
tibble	add_column()

Other functions used in examples

Package	Functions
dplyr	case_when(); across(); select(); if_else()
stringr	str_count(); str_detect()
tidyselect	contains()
janitor	clean_names()
lubridate	interval()
base	months(); round(); ceiling(); as.numeric()
tidyr	separate_rows()

Resources

• https://cran.r-project.org/web/packages/stringr/vignettes/regular-expressions.html
• https://data.library.virginia.edu/working-with-dates-and-time-in-r-using-the-lubridate-package/
• https://r4ds.had.co.nz/dates-and-times.html
• https://cran.r-project.org/web/packages/lubridate/vignettes/lubridate.html
• https://www.tidyverse.org/blog/2019/06/rlang-0-4-0/