[R] as(, "numeric") vs as.numeric()

[Franklin Bretschneider]

Dear Erik Wright,


Re:

> Could someone please explain this R behavior to me:
> 
>> typeof(as.numeric(1:10))
> [1] "double"
>> typeof(as(1:10, "numeric"))
> [1] "integer"
> 
> I expected "double" in both cases.  In the help for the "as" function it says:
> 
> "Methods are pre-defined for coercing any object to one of the basic datatypes. For example, as(x, "numeric") uses the existing as.numeric function."


This happens because 1:10 yields only integers, and so can be stored cheap,
whereas as.numeric() actually means: as.double.
The "numeric" in the second line is an unused argument.

Best regards,

Frank
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Franklin Bretschneider
Dept of Biology
Utrecht University
bretschr at xs4all.nl