What's wrong with as.numeric in R?

Question

> X864291X8X74
[1] 8.0000000000  9.0000000000  10.0000000000 6.0000000000  8.0000000000 
10 Levels: 0.0000000000 10.0000000000 12.0000000000 3.0000000000 4.0000000000 6.0000000000 ... NULL

> as.numeric(X864291X8X74)

[1] 8 9 2 6 8

what did I misunterstood? shouldn't be the result of as.numeric 8 9 10 6 8?

How do I get the correct result?

There is nothing wrong with as.numeric in R. It is working exactly as it should ;) — Ricardo Saporta, Feb 21 '13 at 22:44
Use `hablar::as_reliable_num` which converts the vector to numeric as you expect, i.e. to 8 9 10 6 8. — davsjob, Nov 04 '18 at 11:17

score 27 · Accepted Answer · edited May 23 '17 at 11:47

27

Your vector is a factor. This question has been asked quite a few times, ex: here, here, here. In order to convert a factor to numeric, you'll have to convert to character first. Try:

as.numeric(as.character(my_vec))

edited May 23 '17 at 11:47

Community

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answered Feb 21 '13 at 22:32

Arun

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score 2 · Answer 2 · answered Feb 21 '13 at 22:56

The documentation at ?factor states:

To transform a factor f to approximately its original numeric values, as.numeric(levels(f))[f] is recommended and slightly more efficient than as.numeric(as.character(f)).

So the following works as well:

as.numeric(levels(my_vec))[my_vec]

What's wrong with as.numeric in R?

2 Answers2

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