CODEWITHSUNDEEP
rnatural-logarithm
user24143101
user24143101

Reputation: 13

How to convert a number on the log2 scale to natural log

I need to convert a number in the log2 scale (4.6), to the natural scale.

Using Rmpfr in this example (text doesn't work as there is no way to input my data as base = (natural log). I cannot see any other packages that will allow me to do this. I wonder what it is I am missing. Apologies if this is a very simple question; I'm very new to quantitative research.

Upvotes: 1

Views: 250

Answers (1)

Ben Bolker
Ben Bolker

Reputation: 226332

As pointed out in the comments, there are two ways to do this:

x1 <- log(2^4.6)

first converts the number back from log2 to the unlogged scale (the value is 24.25), then computes its natural logarithm (3.188).

The change-of-base formula uses more math, but is slightly more efficient (especially if you compute the value of log2(exp(1)) (or log(2)) once, store it, and re-use it in multiple calculations).

x2 <- 4.6/log2(exp(1))
## this can also be expressed as:
x3 <- 4.6*log(2)
stopifnot(all.equal(x1, x2))
stopifnot(all.equal(x1, x3))

Upvotes: 4

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