Fitting a function in R

Question

I have a few datapoints (x and y) that seem to have a logarithmic relationship.

> mydata
    x   y
1   0 123
2   2 116
3   4 113
4  15 100
5  48  87
6  75  84         


        

Answer 1

Try taking the log of your response variable and then using lm to fit a linear model:

fit <- lm(log(y) ~ x, data=mydata)

The adjusted R-squared is 0.8486, which at face value isn't bad. You can look at the fit using plot, for example:

plot(fit, which=2)

But perhaps, it's not such a good fit after all:

last_plot() + geom_line(aes(x=x, y=exp(fit$fitted.values)))