Defining functions - an interesting problem

On Wed, 27 May 2009, utkarshsinghal wrote:

I define the following function:
(Please don't wonder about the use of this function, this is just a 
simplified version of my actual function. And please don't spend your 
time in finding an alternate way of doing the same as the following 
does not exactly represent my function. I am only interested in a 
good explanation)

f1 = function(x,ties.method="average")rank(x,ties.method)
f1(c(1,1,2,4), ties.method="min")

[1] 1.5 1.5 3.0 4.0

I don't know why it followed ties.method="average".

Look at the arguments to rank()

args(rank)

function (x, na.last = TRUE, ties.method = c("average", "first",
    "random", "max", "min"))

When you do rank(x, ties.method) you are passing "min" as the second 
argument to rank(), which is the na.last argument, not the ties.method 
argument.  This didn't give an error message because there weren't any 
NAs in your data.

You want
f1 = function(x,ties.method="average")rank(x,ties.method=ties.method)
which gives

f1(c(1,1,2,4), ties.method="min")

[1] 1 1 3 4

    -thomas

Thomas Lumley            Assoc. Professor, Biostatistics
tlumley at u.washington.edu    University of Washington, Seattle