The stats:::cor.test.default function has these tests near the start:
if (length(x) != length(y))
stop("'x' and 'y' must have the same length")
if (!is.numeric(x))
stop("'x' must be a numeric vector")
if (!is.numeric(y))
stop("'y' must be a numeric vector")
I'd like to suggest putting the first test in last place instead, which
would make some user errors easier to diagnose. For example, if I
misspell one of the column names, I get
df <- data.frame(x = 1:10, y = 1:10)
cor.test(df$X, df$y)
#> Error in cor.test.default(df$X, df$y): 'x' and 'y' must have the
same length
because df$X is NULL. It would be more obvious what went wrong if the
error said
Error in cor.test.default(df$X, df$y): 'x' must be a numeric vector
Duncan Murdoch
P.S. An even more friendly error message would give the actual
expression for x instead, i.e.
Error in cor.test.default(df$X, df$y): 'df$X' is not a numeric vector
but that's not the style of error used in most stats functions.
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