[R] a quick question about "rbinom"

[David Winsemius]

On Jan 4, 2012, at 8:46 PM, David Winsemius wrote:

>
> On Jan 4, 2012, at 7:43 PM, Robert Baer wrote:
>
>> -----Original Message----- From: lynn.tsai
>> Sent: Wednesday, January 04, 2012 3:38 PM
>> To: r-help at r-project.org
>> Subject: [R] a quick question about "rbinom"
>>
>> Hello, I have the following code using rbinom, but I don't  
>> understand what
>> *"+1"* means in the code.

It means the author either doesn't know the 'sample' function, or  
wants you to understand how to use 'rbinom', or that's just the way  
she thinks.

>> Could someone help? Thanks so much,
>>
>>> X1<-c("A","B")[rbinom(n,1,0.6)+1]
>>> X2<-c("C","D")[rbinom(n,1,0.1)+1]

C.f.

X1<-sample( c("A","B"), n,  prob= c(0.6, 0.4))
X2<-sample( c("C","D"), n,  prob= c(0.6 ,0.4))

>>
>> It mean index the vector as 1's and 2's  (1st and 2nd item in list)  
>> rather than 0's and 1's because R indices start at 1, not 0.
>
Sorry for the blank message.
-- 

David Winsemius, MD
West Hartford, CT