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Using format() with numbers

The behavior of format() can be pretty confusing, so you'll spend most of this exercise exploring how it works.

Recall from the video, the scientific argument to format() controls whether the numbers are displayed in fixed (scientific = FALSE) or scientific (scientific = TRUE) format.

When the representation is scientific, the digits argument is the number of digits before the exponent. When the representation is fixed, digits controls the significant digits used for the smallest (in magnitude) number. Each other number will be formatted to match the number of decimal places in the smallest number. This means the number of decimal places you get in your output depends on all the values you are formatting!

For example, if the smallest number is 0.0011, and digits = 1, then 0.0011 requires 3 places after the decimal to represent it to 1 significant digit, 0.001. Every other number will be formatted to 3 places after the decimal point.

So, how many decimal places will you get if 1.0011 is the smallest number? You'll find out in this exercise.

This is a part of the course

“String Manipulation with stringr in R”

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Exercise instructions

  • Format c(0.0011, 0.011, 1) with digits = 1. This is like the example described above.
  • Now, format c(1.0011, 2.011, 1) with digits = 1. Try to predict what you might get before you try it.
  • Format percent_change by choosing the digits argument so that the values are presented with one place after the decimal point.
  • Format income by choosing the digits argument so that the values are presented as whole numbers (i.e. no places after the decimal point).
  • Format p_values using a fixed representation.

Hands-on interactive exercise

Have a go at this exercise by completing this sample code.

# Some vectors of numbers
percent_change  <- c(4, -1.91, 3.00, -5.002)
income <-  c(72.19, 1030.18, 10291.93, 1189192.18)
p_values <- c(0.12, 0.98, 0.0000191, 0.00000000002)

# Format c(0.0011, 0.011, 1) with digits = 1
___

# Format c(1.0011, 2.011, 1) with digits = 1
___

# Format percent_change to one place after the decimal point
___

# Format income to whole numbers
___

# Format p_values in fixed format
___
Edit and Run Code

This exercise is part of the course

String Manipulation with stringr in R

IntermediateSkill Level
4.4+
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Learn how to pull character strings apart, put them back together and use the stringr package.

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You'll start with some basics: how to enter strings in R, how to control how numbers are transformed to strings, and finally how to combine strings together to produce output that combines text and nicely formatted numbers.

Exercise 1: Welcome!Exercise 2: QuotesExercise 3: What you see isn't always what you haveExercise 4: Escape sequencesExercise 5: Turning numbers into stringsExercise 6: Using format() with numbers
Exercise 7: Controlling other aspects of the stringExercise 8: formatC()Exercise 9: Putting strings togetherExercise 10: Annotation of numbersExercise 11: A very simple tableExercise 12: Let's order pizza!

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