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R4DS Study Group - Week 5

Pierrette Lo 5/1/2020

This week’s assignment

  • Chapters 4, 6, 8
  • Additional reading on R Markdown

As always, start by loading {tidyverse}

library(tidyverse)

Ch 4: Workflow - basics

Exercises

  1. Why does this code not work?
my_variable <- 10
my_varıable
## [1] 10

It’s subtle - in the second line, the “i” is actually a different character (“ı”).

Oddly, I did not get an error message - it’s possible that the font I’m using in RStudio (Fira Code) recognizes both of those characters as being the same.

Regardless, the point is that you can get tripped up by extremely subtle typos (missing parentheses, commas, etc.). It’s frustrating at first but your eyes and brain will adapt eventually!

  1. Tweak each of the following R commands so that they run correctly:
ggplot(dota = mpg) + 
  geom_point(mapping = aes(x = displ, y = hwy))
## Error in FUN(X[[i]], ...): object 'displ' not found


fliter(mpg, cyl = 8)
## Error in fliter(mpg, cyl = 8): could not find function "fliter"

filter(diamond, carat > 3)
## Error in filter(diamond, carat > 3): object 'diamond' not found

There are typos in all 3 of these commands. If you get an “object not found” error, it usually means either you’ve forgotten to define the object earlier in your code, or you’ve made a typo somewhere.

If “object not found” refers to a column in your dataset, it could mean an error relating to your column name, or an error relating to your dataset.

There is an additional error in the filtering of mpg - you need the double equals sign == to test for equality. The single equals sign is an assignment operator similar to <-.

  1. Press Alt + Shift + K. What happens? How can you get to the same place using the menus?

This brings up the keyboard shortcuts menu. You can also access the list of shortcuts by going to the “Tools” menu and selecting “Keyboard Shortcuts Help”.

Ch 6: Workflow - scripts

Notes

  • Script = code focused. Mark comments with #
  • R Notebook = code + plain text. Mark comments in code chunks with #, or just type in the text area
  • R Markdown = similar to R Notebook but you can set it up to knit into a web page, PDF, Word doc, slides, etc.
  1. Go to the RStudio Tips twitter account, https://twitter.com/rstudiotips and find one tip that looks interesting. Practice using it!

General note - the R community is super active on Twitter. Follow #rstats for news, tips, example projects, commiseration, and more from beginners to experts.

Follow #tidytuesday to see what everyone (beginners to experts) is doing with the weekly Tidy Tuesday dataset.

  1. What other common mistakes will RStudio diagnostics report? Read https://support.rstudio.com/hc/en-us/articles/205753617-Code-Diagnostics to find out.

You can paste the above code for exercise 4.2 into an R script to see what kinds of messages you get when you enable diagnostics.

Ch 8: Workflow - projects

Notes

  • If you just open RStudio by clicking on the icon, it loads the last project you had open (not sure what loads if you’ve never used projects)
  • You can check your working directory by looking at the bar just under the Console tab
  • Click on the little arrow beside the directory to open that folder in the Files tab (should load by default when you open the project, but in case you navigated away and need to get back to it)
  • Don’t save projects or files in the directories that your R or RStudio software are installed in

screenshot

Demo

Create a new R Project to use for your R4DS files.

R Markdown readings

  • Let’s save the R Markdown discussion for a future meeting so we can get back to working with data.