R help - Jun 2009 - Error "the condition has length > 1 and only the first element will be used"

Ahoy. I'm trying to run a function for each country in a multinational  
dataset. Keeping it simple, an example is


for(j in 11:14) {
if(data$country_str == "j") {

mu <- mean(data$ecdfs1)
} else {
mu <- 0
}
}

The number of countries is greater and the functions are more complex, but  
this fails just the same. The consistent error is


In if (data$country_str == "j") { :
   the condition has length > 1 and only the first element will be used

Using the inelegantly workable

if(data$country_str == "11") {

mu <- mean(data$ecdfs1)
} else {
mu <- 0
}

And repeating manually I still get the same error.

For those who know both, in Stata I did this with the foreach command (but  
I don't trust Stata's results for my ML estimates), although for summary
statistics the bysort command would be appropriate. I can't find a clear  
analog in R.

Can anybody explain just what the error is, and how to fix it? Which  
'condition' is inappropriately lengthed - the country string or the
values
it takes?

Neither the  manual nor examples online match my problem - or at least not  
apparently to me. I've tried an ifelse but it runs the functions for every  
observation depending upon whether or not the condition is met. I only  
want 13 sets of output, not 30,000.

Do I need to just break my dataset up into the countries and do it the  
long way?


Much appreciated, thank you.

Casey

Hi

r-help-bounces at r-project.org napsal dne 19.06.2009 09:26:57:
> Ahoy. I'm trying to run a function for each country in a multinational 
> dataset. Keeping it simple, an example is
> 
> 
> for(j in 11:14) {
> if(data$country_str == "j") {
> 
> mu <- mean(data$ecdfs1)
> } else {
> mu <- 0
> }
> }
> 
First few guesses

data is a data frame with more than one row.
data$country_str is a vector of country strings like in state.abb
data$ecdfs1 are some numeric data
you want to compute ecdfs1 mean for each country_str

If yes then maybe

aggregate(data$ecdfs1, list(data$country_str), mean)

could do it

If some of above is not valid so please give some more info to poor 
helpers.

Besides, the error comes from

?"if"

cond
A length-one logical vector that is not NA. 
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Conditions of length greater than one are accepted with a warning, but 
only the first element is used. Other types are coerced to logical if 
possible, ignoring any class. 

For comparing vectors use ifelse instead

Regards
Petr


> The number of countries is greater and the functions are more complex, 
but 
> this fails just the same. The consistent error is
> 
> 
> In if (data$country_str == "j") { :
>    the condition has length > 1 and only the first element will be used
> 
> Using the inelegantly workable
> 
> if(data$country_str == "11") {
> 
> mu <- mean(data$ecdfs1)
> } else {
> mu <- 0
> }
> 
> And repeating manually I still get the same error.
> 
> For those who know both, in Stata I did this with the foreach command 
(but 
> I don't trust Stata's results for my ML estimates), although for
summary
 
> statistics the bysort command would be appropriate. I can't find a
clear
 
> analog in R.
> 
> Can anybody explain just what the error is, and how to fix it? Which 
> 'condition' is inappropriately lengthed - the country string or the
values 
> it takes?
> 
> Neither the  manual nor examples online match my problem - or at least 
not 
> apparently to me. I've tried an ifelse but it runs the functions for 
every 
> observation depending upon whether or not the condition is met. I only 
> want 13 sets of output, not 30,000.
> 
> Do I need to just break my dataset up into the countries and do it the 
> long way?
> 
> 
> Much appreciated, thank you.
> 
> Casey
> 
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