Duncan Murdoch wrote:
On 07/03/2010 5:26 PM, rkevinbur...@charter.net wrote:
Thatnk you.

The documentation indicates as you indicated that if there is not an exact 
match then the next element is chosen. But it does not indicate the case that 
contains an exact match but there is not value to be returned (=, case). From 
what you indicate this is treated as if it was not a match.

I think the writing is not very clear (and Brian Ripley has improved it in R-devel), but it does intend to say:

  - If there is an exact match with a value, then that value is returned.

Re-reading it, I think my clarification is unclear. The matching occurs to the argument name. I should have written:

- If there is an exact match to an argument name with an associated value, then that value is returned.

Duncan Murdoch
- If there is an exact match with no value, then the next value is returned. - If there is no match, then the 1st unnamed arg (or 2nd if EXPR isn't named) is returned.

I think this is different from your interpretation.

Duncan Murdoch

Kevin

---- Uwe Ligges <lig...@statistik.tu-dortmund.de> wrote:
On 06.03.2010 21:49, rkevinbur...@charter.net wrote:
In browsing the source I see the following construct:

     res<- switch(type, working = , response = r, deviance = ,
         pearson = if (is.null(object$weights))
             r
         else r * sqrt(object$weights), partial = r)

I understand that 'switch' will execute the code that is matched by its corresponding 
string value (in this case 'type'). What I don't understand is the empty code. Is this 
code saying that if the type is "deviance" then fill the 'res' variable with an 
empty value? From my naive point of view it seems that 'res' will only get a value(s) if 
'type' is 'response', 'pearson', or 'partial'. Please help with my understanding.
Please do read the help pages!

 From ?switch:

"If there is an exact match then that element is evaluated and returned if there is one, otherwise the next element is chosen, [...]"

Example:

switch("A", A=1, B=, C=2) # 1
switch("B", A=1, B=, C=2) # 2

Uwe Ligges



Kevin Burton
rkevinbur...@charter.net

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