The antilog (or inverse logarithm) is the process of finding the original value from its logarithmic representation. If you have log(x) = y, then antilog(y) = x. In practical data analysis, you’ll encounter this often when working with log-transformed data and need to reverse the transformation to get back to the original scale.
In R, you have multiple ways to calculate antilogs depending on the logarithm base used:
Quick Reference:
- Base 10: Use
10^value - Natural log (base e): Use
exp(value) - Custom base: Use
base^value
Why Calculate Antilogs?
You commonly need antilogs when:
- Reversing log-transformed data for interpretation
- Converting from logarithmic scale back to original units
- Analyzing ratios or growth rates that were log-transformed
- Working with odds ratios in statistical modeling
Let me show you how to find antilog of values in R with practical examples.
Calculate Antilog of a Value Using Base 10
Let’s see how we can use base 10 to find antilog of value:
# Declare number
number = 2
# Take base 10
log_number = log10(number)
# Show log value
print(log_number)
# Take antilog
x <- 10^log_number
# Print antilog value
print(x)
Output:
[1] 0.30103
[1] 2
Here the output shows log and antilog value for number 2 which calculated using base 10.
Calculate Antilog of a Value Using exp() Function
Let’s see how we can use exp() function to find antilog of number:
# Declare number
number = 2
# Take log values of number
log_number <- log(number)
# Show log number
print(log_number)
# Take antilog
x <- exp(log_number)
# Print antilog value
print(x)
Output:
[1] 0.6931472
[1] 2
Here the output shows log and antilog values for number 3 which calculated using exp() function.
You can calculate the antilog value with any base value.
# Declare number
number = 8
# Take log number
log_number <- log(number,5)
# Show log number
print(log_number)
# Take antilog
x <- 5^log_number
# Print antilog value
print(x)
Output:
[1] 1.29203
[1] 8
Here the output shows log and antilog value for number 8 with base 5.