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I have a very basic question concerning a glmnet plot, but somehow am not able to explain it to myself.

Currently, I work through the glmnet vignette.

I stumbled upon the following example:

cvfit = cv.glmnet(x, y)
plot(cvfit)

enter image description here

Note that the minimum lambda found is 0.08307. This value should be represented at the x-axis of the plot at the left dotted vertical line.

However, when I calculate, I get $\log(0.08307)= -1.080555$.

This is different to (ca.) -2.5 shown by the plot.

Any ideas why the plot shows other values? What am I getting wrong here?

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  • $\begingroup$ I think you'll get more answers if you edit your question and state explicitly that this is about the R package glmnet (web.stanford.edu/~hastie/glmnet/glmnet_alpha.html), and give a small reproducible example (i.e. a small, self-contained piece of code that produces the problem you describe) $\endgroup$
    – Adrian
    Jun 3, 2016 at 9:40
  • $\begingroup$ Thx for the advice. $\endgroup$
    – Toby_Shoby
    Jun 3, 2016 at 10:01

1 Answer 1

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In statistics, unless otherwise specified, "log" usually means the natural logarithm. Your mistake was that you calculated the base-10 logarithm instead. The natural log of 0.08307 is about -2.49.

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    $\begingroup$ Thank you very much, I knew it was something pretty basic. $\endgroup$
    – Toby_Shoby
    Jun 3, 2016 at 10:58

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