Re: [R] vector manipulations

From: <Bill.Venables_at_csiro.au>
Date: Wed, 05 Mar 2008 08:41:28 +1000

Your problem is that your function log1( , ) is not vectorized with respect to its arguments. For a function to work in outer(...) it must accept vectors for its first two arguments and it must produce a parallel vector of responses.

To quote the help information for outer:

"FUN is called with these two extended vectors as arguments. Therefore,
it must be a vectorized function (or the name of one), expecting at least two arguments."

Sometimes Vectorize can be used to make a non-vectorized function into a vectorized one, but the results are not always entirely satisfactory in my experience. See

?Vectorize

Bill Venables
CSIRO Laboratories
PO Box 120, Cleveland, 4163
AUSTRALIA

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-----Original Message-----
From: r-help-bounces_at_r-project.org [mailto:r-help-bounces_at_r-project.org] On Behalf Of Pete Dorothy
Sent: Wednesday, 5 March 2008 3:38 AM
To: r-help_at_r-project.org
Subject: [R] vector manipulations

Hello,

I have simulated a set of data which i called "nir" (a vector).

I have created a function "logl" which calculates the log-likelihood.

logl is a function of 2 real parameters : "beta" and "zeta" (of length 1).

This function works perfectly well when I try for example
"logl(0.1,0.2)"

Now if I try :

x <- seq(0.1, 0.5, by = 0.1)
y <- seq(0.1, 0.5, by = 0.1)
z <- outer(x, y, logl)"

I get an error.

The problem seems to be that inside "logl", the following expression is calculated : "sum( log( beta+(nir-1)*zeta ) )". So it is a vector manipulation. The error tells me that "nir" is not the size of "zeta". Yet
usually it is no problem since "length(zeta)=1".

When I replace "sum( log( beta+(nir-1)*zeta ) )" by a loop, I get no mistake. But I think it slows down the program.

Do you have an idea where the problem is ?

Thank you very much.

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