Create a one-way frequency table

You want to create a one-way frequency table from a categorical column in a data frame. One-way frequency tables show the distribution of a categorical variable.

Step 1 - Start with the data frame.

Step 2 - Ensure the data frame is tidy. The variable you want to appear in the frequency table should be in its own column.

Step 3 - Then use janitor::tabyl() to create the frequency table.

data %>% 
  tabyl(col_1)

Step 4 (Optional) - Format the percent column using janitor::adorn_pct_formatting().

data %>% 
  tabyl(col_1) %>% 
  adorn_pct_formatting()

Example

fda_adverse describes adverse events that have been reported to the FDA for various drugs. We are interested in the outcome column, which describes the long-term outcome for the individuals who reported each event.

To begin, we first load the janitor package. Then we pass the data frame fda_adverse to tabyl() and then call our variable of interest: outcome.

library(janitor)
fda_adverse %>% 
  tabyl(outcome)

                 outcome    n    percent
                   fatal  277 0.04804857
           not recovered  966 0.16756288
               recovered 2020 0.35039029
 recovered with sequelae   82 0.01422376
              recovering  980 0.16999133
                 unknown 1440 0.24978317

Finally, we format the percent column so the values look like percentages.

fda_adverse %>% 
  tabyl(outcome) %>% 
  adorn_pct_formatting()

                 outcome    n percent
                   fatal  277    4.8%
           not recovered  966   16.8%
               recovered 2020   35.0%
 recovered with sequelae   82    1.4%
              recovering  980   17.0%
                 unknown 1440   25.0%

From this table we can see how many adverse events fell into each outcome category. For example, the majority of adverse events have the outcome of recovered, with \(2020\) events, which is \(35\)% of the event outcomes.

Frequency tables and SAS

Frequency tables are obtained in SAS using the FREQ procedure with the TABLES statement.

In SAS:

PROC FREQ DATA = data;
  TABLES col_1 / NOCUM;
RUN;

In R:

data %>% 
  tabyl(col_1) %>% 
  adorn_pct_formatting()