[R] shift and pop equivalent in R

[Xie Chao]

Thanks Barry for the code sample, and Thanks Duncan for the clarification.

Both replies help a lot!

Best Regards,
Xie Chao


On Wed, Apr 21, 2010 at 2:50 AM, Barry Rowlingson
<b.rowlingson at lancaster.ac.uk> wrote:
> On Tue, Apr 20, 2010 at 7:03 PM, Xie Chao <xiechaos at gmail.com> wrote:
>> Dear All,
>>
>> I am wondering is there any shift (or pop or push or unshift) equivalent in R?
>> For example,
>> shift(x)   # should return x[1], and x becomes x[-1]
>>
>
>  I seem to have implemented a FIFO stack in 2003:
>
> http://finzi.psych.upenn.edu/R/Rhelp02/archive/15541.html
>
>  but note the reply commenting on the existence of the "stack"
> function in R which stacks data on top of other data.
>
> Here's sample usage once you've loaded the code from that old posting:
>
>> s=stack()
>> push(s,1)
>> s
> [[1]]
> [1] 1
>
>> push(s,3)
>> push(s,4)
>> pop(s)
> [1] 4
>> pop(s)
> [1] 3
>> s
> [[1]]
> [1] 1
>
>  If you want to implement a 'shift' method, just look at the existing
> pop and push methods and write something similar. Note how the
> functions are created on the object, and then called from S3 methods.
> Note the use of <<- within the functions on the object. There's
> probably better ways to do this, and with S4 methods.
>
> Barry
>
>
>
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