[R] help

[(Ted Harding)]

On 28-Jul-09 08:28:22, Inchallah Yarab wrote:
> How I can vary the parameters for a function? 
> 
> I have a function with 5 parameters I want to turn the function for a
> range of numbers for one of these parameters!! i want to have in the
> end the value of the function in the different cas of one of the
> paramter (the others paramters are fixes!!) thank you for your help

It depends on the internals of the function. In R, most functions
(including what you write yourself, if written in the right way)
allow you to give a vector of numbers to a numerical parameter.
The calculations are then "vectorised" in a single pass, and the
results for each value are returned as a vector.

For example, the pnorm() function for several different standard
deviations:

  SD = c(1,1.5,2,2.5,3)
  cbind(SD,pnorm(q=0.5, mean=0, sd=SD))
  # [1,] 1.0 0.6914625
  # [2,] 1.5 0.6305587
  # [3,] 2.0 0.5987063
  # [4,] 2.5 0.5792597
  # [5,] 3.0 0.5661838

Likewise, if your function is

  my.fun <- function(par1,par2,par3,par4,par5){
    (par1 + par2*par3 + (par3^2)*(par4 + par5))
  }

then you could have

  par1 <- 1.1 ; par2 <- 1.2 ; par4 <- 1.4; par5 <- 1.5
  par3 <- SD # (as above)
  cbind(SD,my.fun(par1,par2,par3,par4,par5))
  #       SD       
  # [1,] 1.0  5.200
  # [2,] 1.5  9.425
  # [3,] 2.0 15.100
  # [4,] 2.5 22.225
  # [5,] 3.0 30.800

Hoping this helps!
Ted.

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E-Mail: (Ted Harding) <Ted.Harding at manchester.ac.uk>
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Date: 28-Jul-09                                       Time: 15:39:27
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