rnonlinear-functionsnatural-logarithm

R: Using equation with natural logarithm in nls


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!


Solution

  • 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(5)
    ## [1] 0.69897
    

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