In cknotz/bst290: An R Package To Complement the BST290 (UiS) Course

library(learnr)
library(dplyr)
library(magrittr)
library(bst290)

data(ess)
knitr::opts_chunk$set(echo = FALSE)

Data cleaning & management

De-bugging exercises {data-progressive=TRUE}

Here are again some exercises that require you to fix problems with code chunks. Hint: Look for typos, missing or misplaced symbols, and check the parentheses.

Problem No. 1

In this scenario, you want to select three variables from the ess dataset, but all you get is an error message:

ess %>% 
  select(idno,gndr,agea

**Hint:** Everything that is opened must also be closed...

Problem No. 1: Solution

The last closing parenthesis was of course missing.

ess %>% 
  select(idno,gndr,agea)

Problem No. 2

Now you want to link two operations, where the first selects variables and the second filters observations. But, again, something does not work:

ess %>% 
  select(idno,cntry,agea,vote,stflife)
  filter(agea>=25)

**Hint:** Check if there are any missing symbols or operators.

Problem No. 2: Solution

The problem was that the pipe operator was missing at the end of the select()-line, and R did not understand that the operations should be linked together:

ess %>% 
  select(idno,cntry,agea,vote,stflife) %>% 
  filter(agea>=25)

Problem No. 3

Here you want to filter the data so that only women are left (where gndr is equal to Female), but somehow R refuses to do what you want:

ess %>% 
  filter(gndr="Female")

**Hint:** How do you tell `R` that two things *should* be equal?

Problem No. 3: Solution

The problem was with the equal signs: If you want tell R that something should or has to be equal to something else, you always use double equal signs (==).

ess %>% 
  filter(gndr=="Female")

Problem No. 4

OK, this one might be a bit mean --- but maybe you can figure it out anyways?

You want to select some variables from the ess dataset, this time without using the pipe but by specifying the dataset explicitly in the select() command:

select(data = ess,
       agea,idno,gndr)

**Hint:** Take a close look at the `data=ess` part --- there was a special thing about `select()` and `filter()` where you had to use a specific punctuation symbol...

Problem No. 4: Solution

The problem was the special way you name the dataset you want to use in select() (or also filter()): You have to add a dot before data so that it reads .data = ess, not data = ess:

select(.data = ess,
       agea,idno,gndr)

A more convenient alternative is to use the pipe operator from the start:

ess %>% 
  select(agea,idno,gndr)

Conclusion

That is it for this part! Next: Data visualization!

cknotz/bst290 documentation built on Nov. 11, 2023, 1 p.m.