[R] How to modify function for list

[Chung-hong Chan]

Dear R Gurus,

I have a function which calculate the BMI standard deviation score
based on the age and gender specific L, M, S value.
I have written a function like this

bmisds <- function (age, gender, bmi){
  if (age ==1 & gender ==1)
    {
      bmif <- c(-1.013,16.133,0.07656)
    }
  else if (age ==1 & gender ==0)
    {
      bmif <- c(-1.79,16.421,0.07149)
    }
  else if (age == 2 & gender == 1)
    {
      bmif <- c(-1.403,15.58,0.07342)
    }
  else if (age == 2 & gender == 0)
    {
      bmif <- c(-2.045,15.861,0.07116)
    }
....

      (((bmi/bmif[2])**bmif[1] -1)/(bmif[1]*bmif[3]))
}

This function work when I supply a single variable, e.g. bmisds(1,0,16)

When I try it with a list, e.g.
age <- c(12,13,14)
gender <- c(0,1,1)
bmi <- c(14,15,16)
bmisds(age,gender,bmi)

This function give me wrong answer and error msg.
Warning messages:
1: the condition has length > 1 and only the first element will be
used in: if (age == 1 & gender == 1) {


How can I midify this function to work with list/vector?

regards,
C


-- 
CH Chan
Research Assistant - KWH
http://www.macgrass.com