Thanks for the informative comments and the detailed explanation.
----- Original Message ----- From: "Adaikalavan Ramasamy" <[EMAIL PROTECTED]>
To: "Feng Chen" <[EMAIL PROTECTED]>
Cc: "R-help" <r-help@stat.math.ethz.ch>
Sent: Tuesday, March 01, 2005 12:25 AM
Subject: Re: [R] A problem about outer()
You might want to read (or re-read) the posting guide about giving a simple example. See comments below.
Henceafter, I won't post any question before: 1. searching the documentation, 2. googling the web, 3. reading the code of the relevant functions, and 4. a careful rereading of the posting guide.
On Mon, 2005-02-28 at 23:03 +0800, Feng Chen wrote:Dear all,
I have something about function outer() that I can't understand. Just see the following example. The two NaNs are due to 0/0, but I can't figure out the cause of the last two errors. I wonder if some one can explain this for me.
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> sx=rbinom(10,1,0.5);ot=rbinom(10,1,0.5);ag <- rbinom(10,100,0.3);ho > <- rbinom(10,100,0.5)
Cute but unfortunately not very legible. Why are you mixing "=" and "<-" ? Is there a problem with space bars and return key on your
I am not sure about the reason for that mixture. Perhaps because "=" and "_" are so close on the keyboard. Anyway, they were definitely not made so by intention.
keyboard ? Please learn to wrap the emails at about 72 characters per line (see http://expita.com/nomime.html).
Thanks, I have followed the instructions listed on that page.
> dp <- > function(s,a,h)sum((sx==s)&(ag==a)&(ho==h)&(ot==1))/sum((sx==s)&(ag==a)&(ho==h))
> (function(x,y)dp(1,x,y))(2,3) [1] NaN > (function(x,y)dp(0,x,y))(27,52) [1] NaN
Again this is confusing. Why not define another function (you will need
Here just for testing pupose. I thought I just need that once (in the outer() function).
to anyway - see below).
Alternatively, you can set 1 as the default value for s in dp().
> dpm <- outer(ag,ho,function(x,y)dp(1,x,y)) Error in outer(ag, ho, function(x, y) dp(1, x, y)) : dim<- : dims [product 100] do not match the length of object [1]
From help("outer") :
'FUN' must be a function (or the name of it) which expects at least two arguments and which operates elementwise on arrays.
And following the suggestion of Prof. Daalgard in the thread http://tolstoy.newcastle.edu.au/R/help/00a/1445.html
dp.vect <- function(s, x, y){ sapply( 1:length(x), function(i) dp( s=s, a=x[i], h=y[i]) ) } outer(ag, ho, FUN=dp.vect, s=1 ) # works but I leave the verification to you
It does work.
Your problem could be generalised as the following example
one <- rnorm(3); two <- rnorm(4) # data outer( one, two, function(x, y) x + y ) # works fine outer( one, two, function(x, y) sum(c(x, y)) ) # does not work
I had tried this before posting.
sum.vect <- function(x, y){ sapply( 1:length(x), function(i) sum( c( x[i], y[i] ) ) ) } outer( one, two, sum.vect )
You have thoroughly explained away my confusion. Thanks for your great patience.
Thank all for being so tolerant and friendly to newcomers.
> dpf <- outer(ag,ho,function(x,y)dp(0,x,y)) Error in outer(ag, ho, function(x, y) dp(0, x, y)) : dim<- : dims [product 100] do not match the length of object [1] > -------------------------------------------------------------------------------------------------------------------
Thanks very much, Feng
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