[R] Variable names AS variable names?

[David Winsemius]

On Feb 25, 2011, at 12:33 PM, Noah Silverman wrote:

> My actual code is several things with adaptive filtering.  This will
> require accessing data sporadically.  The loop was just a quick  
> example
> for the e-mail.
>
> One application is to work with online (streaming) data.  If I get a  
> new
> data point in for code "a1", I'll need to be able to reference the
> matrix named "a1".

So, how do these things you are calling "codes" get their names?

("code" is not an R datatype. a1 is a matrix,  "a1" is a character  
value and it would be returned by names(a1).  )

a1 <- matrix(rnorm(100), nrow=10)
b24 <- matrix(rnorm(100), nrow=10)
q99 <- matrix(rnorm(100), nrow=10)

codes <- list(a1=a1, b24=b24, q99=q99)

str(codes[['a1']])
  ... should be a matrix

Assignment also works with "[[" or with "[".

We really _do_ need  examples that represent the problems posed on the  
list. You have been posting a sufficient number of times to have  
understood this by now.

-- David


>
> On 2/25/11 12:23 AM, David Winsemius wrote:
>>
>> On Feb 25, 2011, at 1:55 AM, Noah Silverman wrote:
>>
>>> How can I dynamically use a variable as the name for another  
>>> variable?
>>>
>>> I realize this sounds cryptic, so an example is best:
>>>
>>> #Start with an array of "codes"
>>>
>>
>> Is there some reason not to use list(a1, b24, q99)? If not then:
>>
>> lapply(codes, somefun)
>>
>>
>>>
>>> #Each code has a corresponding matrix (could be vector)
>>> a1 <- matrix(rnorm(100), nrow=10)
>>> b24 <- matrix(rnorm(100), nrow=10)
>>> q99 <- matrix(rnorm(100), nrow=10)
>>>
>>> #Now, I want to loop through all the codes and do something with  
>>> each
>>> matrix
>>> for(code in codes){
>>>   #here is where I'm stuck.  I don't want the value of code, but the
>>> variable who's name is the value of code
>>>
>>> }
>>>
>>>
>>> Any suggestions?
>>>
>>> -N
>>>

David Winsemius, MD
West Hartford, CT