Knowledge Quiz: Data Frames

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Consider the following data frame, df.

   name age height  eyes
1   bob  25    180 green
2  mike  23    178 green
3  mark  24    169  blue
4 steve  26    183 brown

How can we extract the name column and return the selection as a character vector?

df["name", ]df$namedf[1:2]df[ , "name"]df[1]

• Wrong: This command will try to return a row called “name” and fail because there is no such row in df.
• Correct
• Wrong: This command will return the name and age columns as a \(4 \times 2\) data frame.
• Correct
• Wrong: This command will return the name column as a one-column data frame.

Consider the following data frame, df.

   name age height  eyes
1   bob  25    180 green
2  mike  23    178 green
3  mark  24    169  blue
4 steve  26    183 brown

How can we extract the height column and return the selection as a data frame?

df[[2]]df["height"]df[3]df[ , 3]df[[3]]

• Wrong: This command will return the age column as a numeric vector.
• Correct
• Correct
• Wrong: This command will return the height column as a numeric vector.
• Wrong: This command will return the height column as a numeric vector.