Hi All,
I meant to take the min row by row. But the result is apparently not
what I want. Changing min to pmin solve the problem.
> df=data.frame(X=1:10, Y=1:10)
> transform(df, Z=min(X,10-Y))
X Y Z
1 1 1 0
2 2 2 0
3 3 3 0
4 4 4 0
5 5 5 0
6 6 6 0
7 7 7 0
8 8 8 0
9 9 9 0
10 10 10 0
I try to look at the source code to understand what transform() does.
I know that ` can be used to refer to a column in a data.frame. But I
don't understand what the usage of `_data` in transform.data.frame.
Could you please help me understand what `_data` means and min doesn't
work row by row?
> transform.data.frame
function (`_data`, ...)
{
e <- eval(substitute(list(...)), `_data`, parent.frame())
tags <- names(e)
inx <- match(tags, names(`_data`))
matched <- !is.na(inx)
if (any(matched)) {
`_data`[inx[matched]] <- e[matched]
`_data` <- data.frame(`_data`)
}
if (!all(matched))
do.call("data.frame", c(list(`_data`), e[!matched]))
else `_data`
}
<environment: namespace:base>
--
Tom
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