Statistical Computing, 36-350
Tuesday April 17, 2018
traceback(), print() and browser() can help you understand how your function is behaving at different points in time during the computations.assert_that() help ensure that the inputs to your function are correct, so your function can proceed without errors.test_that() give a recorded list of simple properties you want your function to display, so you can ensure that it works correctly as you futher modify your code.“The person who knows the most about your code is you-six-months-ago, and you-six-months-ago are not replying to your emailed questions.” -Anon.
The features of version control:
Complete record of changes allowing you to, e.g., revert back to a previous version of your code if things have gone awry.
Store messages for every change, so that you can recall the rationale for a change later.
With, e.g., Git, you can back your code remotely (e.g., on GitHub), allowing for easy distribution.
Facilitates collaboration; changes can be developed independently and merged together.
Version control tools were designed for “code”, but are useful for all sorts of files (e.g. text reports for 36-401).
Git allows you to take “snapshots” of the contents of a folder on your machine as you make changes to them. Fix a bug? Take a snapshot. Add functionality? Take a snapshot. These snapshots are dubbed commits. Snapshot details are stored in the subfolder .git.
devtools::install_github()If you do not have a GitHub account, get one at github.com.
If you do not have Git installed on your laptop, install it!
Linux: Use your package manager
Mac: Git for Mac (at https://git-scm.com/downloads) or via homebrew (brew install git)
Windows: Git for Windows (at https://git-scm.com/downloads)
During setup, configure Git with your user name (use your full name, not your Andrew ID) and your user email (which should be the same one you used to sign up for your GitHub account).
For this lab, we will follow the paradigm of “GitHub first”. What this means is that when we create a repository, we will create it on GitHub first, then link a local repository to it from inside RStudio.
In GitHub, do the following:
go to the top-level directory (i.e., github.com/<your user name>)
click on “+” at top right, and select “New repository”
name the repository (e.g., “36-350”)
provide a short description of the repository (don’t leave completely blank!)
keep the repository public (as students you have access to free private repos https://education.github.com/pack, but for purposes of this lab keep the repo public)
click on “Initialize this repository with a README”…there is no need to “Add .gitignore” or “Add a license”
click on “Create Repository”
In RStudio, do the following:
click on File > New Project…
click on “Version Control”, then on “Git”
provide the full address for the “Repository URL” (including the https, etc.; by default, this will provide the name of your local repository)
make sure “Create project as subdirectory of:” points to where you want to point it
click on “Create Project”
At this point, you should find that your Files pane is listing the files in your local repository, including one ending in .Rproj and the README.md file that was created on GitHub.
Commits are lists of file changes + new lines + modified lines + deleted lines
The current state of your project is just the accumulated set of file changes over time.
To, e.g., add a new file to your local repository, do the following:
open the new file as you always would (as an R Script, an R Markdown file, etc.)
fill the file with “stuff”
save the file…at this point, the file name should show up in the Git pane next to an “M” symbol (for modified)
continue to modify the file, or…stage the file for a commit by clicking on “Staged” in the Git pane
click on “Commit” in the Git pane
in the new window that opens, add a “Commit message”, then click on the “Commit” button
click on “Push” to push your changes from your local repo to your GitHub repo
Done.
Commit messages exist for your benefit:
Remember that the reader (usually you) will not have full context
In Git, two commits can be merged by applying the relevant changes one after the other.
If the changes are independent this is straightforward.
If the changes conflict it needs to be manually merged (typically due to incompatible changes).
Happy Git With R by Jenny Bryan and a squad of TAs
Pro Git by Scott Chacon & Ben Straub
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