Using math functions

Mathematical functions are an essential part in all computing environments. R provides several groups of basic math functions.

Basic functions

The basic functions include square root, and exponential and logarithm functions as the following table shows:

Note that sqrt() only works with real numbers. If a negative number is supplied, NaN will be produced:

sqrt(-1)
## Warning in sqrt(-1): NaNs produced
## [1] NaN 

In R, numeric values can be finite, infinite (Inf and -Inf), and NaN values. The following code will produce infinite values.

First, produce a positively infinite value:

1 / 0
## [1] Inf 

Then, produce a negatively infinite value:

log(0)
## [1] -Inf 

There are several test functions to check whether a numeric value is finite, infinite, or NaN:

is.finite(1 / 0)
## [1] FALSE
is.infinite(log(0))
## [1] TRUE 

Using is.infinite(), how can we check whether a numeric value is -Inf? Inequality still works with infinite values...