Indexing in Factors
Indexing in factors works the same way as with vectors: you select elements by their position or by a sequence of positions.
Basic Indexing
You can retrieve specific values from a factor by placing their indices inside square brackets.
12345curr_f <- factor(c('USD', 'EUR', 'AUD', 'NOK', 'CHF', 'EUR', 'AUD', 'EUR')) # Output the third and fifth values curr_f[c(3, 5)]
The result shows the selected values, but R still lists all levels of the factor beneath the output.
Dropping Unused Levels
If you want to display only the levels that appear in the result, use the drop = T (T or TRUE) parameter.
12345curr_f <- factor(c('USD', 'EUR', 'AUD', 'NOK', 'CHF', 'EUR', 'AUD', 'EUR')) # Show only levels that appear in the result curr_f[c(3, 5), drop = T]
Sequences
When selecting a range of elements, the colon operator (:) generates consecutive indices. For example, 5:10 creates the sequence 5, 6, 7, 8, 9, 10. This makes it easier to extract multiple elements at once.
Swipe to start coding
You have a dataset of blood types in a factor format. Your task is to:
- Display the 3rd, 10th, and 15th elements of
blood_gr, making sure to drop any unused levels (using thedropparameter). - Show every element from the 15th to the 21st, inclusive.
Solution
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Completion rate improved to 2.27Indexing in Factors
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Indexing in factors works the same way as with vectors: you select elements by their position or by a sequence of positions.
Basic Indexing
You can retrieve specific values from a factor by placing their indices inside square brackets.
12345curr_f <- factor(c('USD', 'EUR', 'AUD', 'NOK', 'CHF', 'EUR', 'AUD', 'EUR')) # Output the third and fifth values curr_f[c(3, 5)]
The result shows the selected values, but R still lists all levels of the factor beneath the output.
Dropping Unused Levels
If you want to display only the levels that appear in the result, use the drop = T (T or TRUE) parameter.
12345curr_f <- factor(c('USD', 'EUR', 'AUD', 'NOK', 'CHF', 'EUR', 'AUD', 'EUR')) # Show only levels that appear in the result curr_f[c(3, 5), drop = T]
Sequences
When selecting a range of elements, the colon operator (:) generates consecutive indices. For example, 5:10 creates the sequence 5, 6, 7, 8, 9, 10. This makes it easier to extract multiple elements at once.
Swipe to start coding
You have a dataset of blood types in a factor format. Your task is to:
- Display the 3rd, 10th, and 15th elements of
blood_gr, making sure to drop any unused levels (using thedropparameter). - Show every element from the 15th to the 21st, inclusive.
Solution
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