R help - Jun 2003 - repeatedly applying function with matrix-rows as argument

Dear R-users,

Suppose I have a function which takes three arguments. I would like to
repeatedly apply the function, using a matrix N*3 in which each row supplies the
three argements for the function. Is this possible? Thank you for your help in
advance!

Kind regards,

Maarten
---------------------------------------------------------------------
  Maarten Speekenbrink
  Psychological Methodology
  Department of Psychology, Faculty of Social and Behavioral Sciences
  address: Roetersstraat 15, 1018 WB Amsterdam, Netherlands
  tel: +31 20 525 6876 / +31 20 525 6870
  fax: +31 20 639 0026

apply(mymatrix, 1, function(x) myfun(x[1], x[2], x[3]))

On Mon, 30 Jun 2003, Maarten Speekenbrink wrote:
> Suppose I have a function which takes three arguments. I would like to
> repeatedly apply the function, using a matrix N*3 in which each row
> supplies the three argements for the function. Is this possible? Thank
> you for your help in advance!
> 
-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

Maarten Speekenbrink wrote:
> Dear R-users,
> 
> Suppose I have a function which takes three arguments. I would like to
repeatedly apply the function, using a matrix N*3 in which each row supplies the
three argements for the function. Is this possible? Thank you for your help in
advance!
> 

  You have a function foo:

 > foo
function(x1,x2,x3){x1+2*x2+3*x3}

  and a 3-column matrix 'm', then do:

 > apply(m,1,function(x){foo(x[1],x[2],x[3])})
  [1] 1.929147 4.695657 4.378048 2.716041 3.835949 4.177343 2.031089 
3.304404
  [9] 1.727687 2.204355

The trick here is to write a function(x) in-line to the apply. This 
function gets one row of the matrix at a time, and calles foo with three 
args.

  You could also write a new function, foo3:

  foo3 <- function(v){ foo(v[1],v[2],v[3])}

  and then apply that:

 > apply(m,1,foo3)
  [1] 1.929147 4.695657 4.378048 2.716041 3.835949 4.177343 2.031089 
3.304404
  [9] 1.727687 2.204355


Baz