[R] FW: why is it numeric(0)?

[luan_sheng]

 yea, I have read the help. But some one tell me that i f you want use a
vector that you don't know it's length, you should use xx=numric(0) , is it
not right? If it isn't right, how can I do?
thanks

-----Original Message-----
From: Douglas Grove [mailto:dgrove at fhcrc.org] 
Sent: Wednesday, June 01, 2005 6:27 AM
To: luan_sheng
Subject: Re: [R] FW: why is it numeric(0)?

Have you read the help page for numeric (?numeric) to understand what it
does?  You should really look at help pages prior to posting.

numeric(x) returns a numeric vector of length x, with all entries
initialized to zero

so numeric(1) returns 0,
numeric(2) returns c(0,0)
etc.

numeric(0) returns a numeric vector of *length 0*, so when you add anything
to it you get the same result (it's basically a numeric NULL)



On Wed, 1 Jun 2005, luan_sheng wrote:

> hello,everyone. I have one question:
> 
> example 1
> > x=numeric(0)
> > y=5
> > print(x+y)
> numeric(0)
>  
> example 2
> > x=numeric(1)
> > y=5
> > print(x+y)
> [1] 5
> 
> why the print(x+y)  is numeric(0) at the first example, but the result 
> is 0 at the second example?
> 
> 
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