Evidence Synthesis Academy

Unite

Back to: Introduction to R

The last tidyr function we will look into is the unite() function. With unite() it will make sense with what we are doing. We will take many columns that share the same type of information and unite them together as 1 column

The above picture displays this idea. We can consider table6 :

## # A tibble: 6 × 4
##       country century  year              rate
##        <fctr>   <chr> <chr>             <chr>
## 1 Afghanistan      19    99      745/19987071
## 2 Afghanistan      20    00     2666/20595360
## 3      Brazil      19    99   37737/172006362
## 4      Brazil      20    00   80488/174504898
## 5       China      19    99 212258/1272915272
## 6       China      20    00 213766/1280428583

It does not make sense to most of us to have a century and year columns but instead to have a 4 digit year. We can use the unite() function to do this:

unite(data,col,..., sep)

where

data is the data frame of interest.

col is the column you wish to add.

... is names of columns you wish to unite together.

sep is how you wish to join the data in the columns.

unite() Example

In our example here we would do the following: `

table6 %>%
    unite("year", century, year, sep="")
## # A tibble: 6 × 3
##       country  year              rate
## *      <fctr> <chr>             <chr>
## 1 Afghanistan  1999      745/19987071
## 2 Afghanistan  2000     2666/20595360
## 3      Brazil  1999   37737/172006362
## 4      Brazil  2000   80488/174504898
## 5       China  1999 212258/1272915272
## 6       China  2000 213766/1280428583

Note that we use quotations around the new column name, but the other two columns century and yearare called in their bare form.

Now we can see that this data is not what we would call tidy yet because the rate column really is not correct. We can fix this with the following code:

table6 %>%
  unite("year", century, year, sep="") %>%
  separate(rate, c("cases", "population")) %>%
  mutate(cases=as.numeric(cases)) %>%
  mutate(population=as.numeric(population)) %>%
  mutate(rate=cases/population)
## # A tibble: 6 × 5
##       country  year  cases population         rate
##        <fctr> <chr>  <dbl>      <dbl>        <dbl>
## 1 Afghanistan  1999    745   19987071 0.0000372741
## 2 Afghanistan  2000   2666   20595360 0.0001294466
## 3      Brazil  1999  37737  172006362 0.0002193930
## 4      Brazil  2000  80488  174504898 0.0004612363
## 5       China  1999 212258 1272915272 0.0001667495
## 6       China  2000 213766 1280428583 0.0001669488

We have not learned about the mutate command but it either replaces a value or adds a value. Note that we can do many things in one step with the piping.

On Your Own: Swirl Practice

In order to learn R you must do R. Follow the steps below in your RStudio console:

1. Run this command to pick the course:

swirl()

You will be promted to choose a course. Type whatever number is in front of 03 Tidy Data. This will then take you to a menu of lessons. For now we will just use lesson 1. Type 1 to choose Tidying Data with tidyr then follow all the instructions until you are finished.

Once you are finished with the lesson come back to this course and continue.


Jessica Kaminsky