extracting-vectors-from-data-frames-R.md

layout	topic	title	language
exercise	dplyr	Extracting vectors from data frames	R

Using the Portal data surveys table (download a copy if it's not in your working directory):

1. Use $ to extract the weight column into a vector
2. Use [] to extract the month column into a vector
3. Extract the hindfoot_length column into a vector and calculate the mean hindfoot length ignoring null values.