Module 03 Summary

What this module established

A data frame is a list whose columns are all the same length; a tibble is the same thing without partial name matching and without dropping to a vector on single-column selection. Use tibbles for new work and expect both.

Carry forward

• The grain — what one row represents — is a decision, and every summary afterwards depends on it. Say it out loud before you group.
• Read the type report on every import. A numeric column arriving as text is evidence about the file, not an inconvenience.
• Run head, glimpse, summary and count before wrangling. They answer four different questions and the NA count only appears in one of them.
• RDS preserves types, factor levels and attributes; CSV does not. Save RDS for your own pipeline and export CSV for other people.

Before moving on

Move on when your import declares its missing markers and you can state how many rows each of your summaries covers.

Mark complete