R String Formatting
A formatted string places values into set slots in a piece of text. sprintf builds such a string from one pattern and the values for its slots.
Text and number slots
The pattern holds one %s slot and two %d slots. The values fill the slots in order.
print(sprintf("%s scored %d of %d", "Ana", 9, 10))Two digits after the point
The %.2f slot rounds the display to two digits. A whole half shows as 2.50 and keeps its trailing zero.
print(sprintf("Pi is about %.2f", 3.14159))
print(sprintf("%.2f", 2.5))Padding with a zero
The %02d slot pads 7 to two digits. The second call builds a time with both parts padded.
print(sprintf("%02d", 7))
print(sprintf("%02d:%02d", 9, 5))A report line from stored values
The values come from three stored names. sprintf places each value in its slot and builds one line.
name <- "Ana"
items <- 3
price <- 1.5
print(sprintf("%s bought %d pens at %.2f each", name, items, price))Example
print(sprintf("%s scored %d of %d (%.1f%%)", "Ana", 9, 10, 90))Key points
- The first value in sprintf is the pattern text.
- A %s slot in the pattern takes a text value.
- A %d slot takes a whole number value.
- The values after the pattern fill the slots in order.
- A %.2f slot shows a number with two digits after the point.
- The %.2f slot rounds the display and leaves the stored value alone.
- A %02d slot pads a short number with a leading zero.
- A %% pair in the pattern prints one percent sign.
In this example one sprintf call builds a full report line. The %% pair at the end prints a single percent sign after the score.
Try it Yourself
Edit the code, then press Run.
Running is simulated · rdrr.io R Snippets
Exercise
What does print(sprintf("%02d", 7)) show?