Posted to another thread a response to this posting ( and to all those who
wanted R on an iPad, I say "forget it"
---------
The if function only takes an argument of length 1 (as the warning says):
?"if"
Many such confusions are resolved by looking at :
?ifelse
--
David
On Nov 1, 2011, at 4:45 PM, "M. Tran" <michellev.tran@gmail.com>
wrote:
> I have a dataset called "results" that looks like this:
>
> arrive depart intercept
> 1 1 1
> 1 2 1
> 1 3 1
> 1 2 2
> 1 3 2
> 1 3 3
> 2 2 2
> 2 3 2
> 3 3 3
>
> where arrive is the period of arrival, depart is the period of departure,
> and intercept is the period in which that person was counted. I'm
trying to
> construct the denominator for a likelihood function using the following
> function. For the first row in "results", for example, I want
the
> denominator to be the sum of all possible arrive/depart combinations an
> interceptor in period 1 could observe: exp(P_1_1) + exp(P_1_2) + exp(P_1_3)
> (i.e. P_arrive_depart).
>
> get_denominator = function(intercept, periods_per_day)
> {
> denominator = array("(", nrow(results))
> for (arrival in 1:periods_per_day)
> {
> for (departure in arrival:periods_per_day)
> {
> while (arrival <= intercept & intercept <= departure)
> {
> addition_to_denom = paste("P", arrival, departure,
sep = "_")
> if (nchar(denominator) == 1)
> {
> denominator = paste(denominator, "exp(",
addition_to_denom, ")", sep > "")
> }
> else
> {
> denominator = paste(denominator, " + exp(",
addition_to_denom, ")", sep > "")
> }
> }
> }
> }
> denominator = paste(denominator, ")")
> return(denominator)
> }
>
>
> denominator = get_denominator(intercept =
results[,"intercept"],
> periods_per_day = 3)
>
>
> I'm getting the following warning message:
>
> In if (arrival <= intercept & intercept <= departure) { ... :
> the condition has length > 1 and only the first element will be used.
>
> As written, the code gives me the denominator for a period 1 interceptor
for
> every single row!
>
> I'm having trouble figuring out how I should re-write this code. Any
> suggestions would be greatly appreciated.
>
>
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/condition-has-length-1-for-LL-denominator-tp3965365p3965365.html
> Sent from the R help mailing list archive at Nabble.com.
>
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> and provide commented, minimal, self-contained, reproducible code.
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