R: Using equation with natural logarithm in nls

Question

Good day,

I am struggling with R and natural logarithm (ln). Firstly, I cannot find a ln(x) function in R. I have noticed that log(x) is the same as ln(x) (when using ln(x) with a calculator).

In R:

log(5) = 1.609438

And with a calculator:

ln(5) = 1.609438
log(5) = 0.69897

I'm trying to fit an equation in R (this is exactly how I found in the literature of 3 references):

y = a + b(^x/₃₀₅) + c(^x/₃₀₅)² + d ln(³⁰⁵/_x) + f ln²(³⁰⁵/_x)

Is it correct to use the following syntax in R to use the equation?

y ~ a + b*(x/305) + c*((x/305)^2) + d*log(305/x) + f*(log(305/x))^2

The idea is to use this function with nls() in R. Thanks in advance!

Answer 1

In R, log is the natural logarithm. In calculators, log usually means base 10 logarithm. To achieve that in R you can use the log10 function.

log(5)
## [1] 1.609438
log10
## [1] 0.69897(5)

As for your formula, it seems correct, since log is the natural logarithm.