Flow and Data
Data Frames
Columns that Travel Together
A data frame keeps related columns aligned by row. New columns can be computed from existing columns.
Program
Play the script to see quantities become row totals, then one grand total.
data_frames.R
sales <- data.frame(item = c("book", "pen"), qty = c(2, 5))
sales$total <- sales$qty * 3
grand_total <- sum(sales$total)
cat(grand_total, "\n", sep = "")
data.frame
`data.frame` creates a table with named columns.
column assignment
`sales$total <- ...` adds or replaces a column.
column sum
`sum(sales$total)` adds all values in one column.