How to plot a linear regression to a double logarithmic R plot?

Question

I have the following data:

someFactor = 500
x = c(1:250)
y = x^-.25 * someFactor

which I show in a double logarithmic plot:

plot(x, y, log="xy")

Now I "find out" the slope of the data using a linear model:

model = lm(log(y) ~ log(x))
model

which gives:

Call:
lm(formula = log(y) ~ log(x))

Coefficients:
(Intercept)       log(x)  
      6.215       -0.250  

Now I'd like to plot the linear regression as a red line, but abline does not work:

abline(model, col="red")

What is the easiest way to add a regression line to my plot?

Answer 1

lines(log(x), exp(predict(model, newdata=list(x=log(x)))) ,col="red")

The range of values for x plotted on the log-scale and for log(x) being used as the independent variable are actually quite different. This will give you the full range:

lines(x, exp(predict(model, newdata=list(x=x))) ,col="red")