character handling: mean() vs sd()
[This article was first published on Odd Hypothesis, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here)
Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.
Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.
Here’s a weird R error/bug/nuance I came across today:
What would you expect the following lines of code to return?
x = c('1', '2', '3')
mean(x)
sd(x) Well, apparently it is:
# mean(x) [1] NA # sd(x) [1] 1
So, sd() silently converts its input to numeric, while mean() does not. More evidence of this is in the source:
> mean
function (x, ...)
UseMethod("mean")
<bytecode: 0x000000001165e790>
<environment: namespace:base>
> sd
function (x, na.rm = FALSE)
sqrt(var(if (is.vector(x)) x else as.double(x), na.rm = na.rm))
<bytecode: 0x000000001158eb00>
<environment: namespace:stats> One hour of my work day was spent sorting this out. You’ve been warned.
Written with StackEdit.
To leave a comment for the author, please follow the link and comment on their blog: Odd Hypothesis.
R-bloggers.com offers daily e-mail updates about R news and tutorials about learning R and many other topics. Click here if you're looking to post or find an R/data-science job.
Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.