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Exercise

Interlude (4)

An alternative method to access the weight data is by referring to its name. In the previous exercises you have been using statements such as cdc$weight to view variables in the data. The dollar-sign tells R to look in cdc for the column called weight.

Now you can combine this technique with what you just learned. You can see the weight for the 567th respondent by typing cdc$weight[567]. Since it's a single vector, you can subset it with just a single index inside square brackets. Similarly, for the first 10 respondents: cdc$weight[1:10].

The command above returns the same result as the cdc[1:10,6] command. Both row-and-column notation and dollar-sign notation are widely used. Which one you choose to use depends on your personal preference.

Instructions

100 XP
  • Assign the smoking status (smoke100) of the 1000th respondent to resp1000_smk.
  • Assign the data containing the height of the first 30 respondents to first30_ht.