vignette: cluster dependence

[adw96]

Hi @svteichman ! Could you please write a (short) vignette demonstrating how to a account for cluster dependence using the cluster argument?

Some suggestions to help guide you

• The closed issue #33 has a basic example -- it would be great if you could expand this into a vignette
• Please mention cage / tank effects as some common sources of cluster dependence
• The vignette should mention that there is anti-conservative inference if cluster dependence isn't accounted for (you can check out the cluster testthat file to see an example)
• Please mention that cluster as an argument exists from v1.2.0.0+ only

As part of this, could you please also amend the code so that cluster can be a character/factor, rather than just a numeric? test-cluster.R has an example (currently commented out) of a test that fails, that I'd love to have pass.

Thanks so much and please let me know if you have any questions! This is not time-sensitive.

[svteichman]

Closing this because it is implemented in PR #58 and merged!