[R] Creating functions with a loop.

[R. Michael Weylandt]

Interpreting your question slightly differently, where ff.k(x) is a
function call.

Suppose you want to get a list of functions like

x^2
x^2 -1
x^2 - 3
x^2 - 6

It's perfectly possible with something like this:

NextFunc <- function(f, i) {
   # Takes in a function f and returns
   # a different function that gives you
   # f(x) - i

   force(i) # probably unnecessary, but good practice as this just
might bite you in a loop


  function(x) f(x) - i
}

Then

f <- function(x) x^2

f2 <- NextFunc(f, 1)

f3 <- NextFunc(f2, 2)

f3(3) # 6 = 3^2 - 1 - 2

Which should be wrappable in a loop.

Michael

On Tue, May 22, 2012 at 11:08 AM, David Winsemius
<dwinsemius at comcast.net> wrote:
>
> On May 22, 2012, at 10:06 AM, Etienne Larrivée-Hardy wrote:
>
>> Hi
>>
>> I am trying to create n functions where each function is defined in
>> function one step before, i.e. something like
>>
>> ff.k(x) = ff.j(x) - sum(1:j),      for j=k-1
>
>
> There is a cumsum function:
>
>> cumsum(1:10)
>  [1]  1  3  6 10 15 21 28 36 45 55
>
> Did you mean something like?:
>
>  ff.k[j] <- ff.j[j] - sum(1:j),      for j=k-1
>
> In R the paren, "(", indicates that you are calling a function whereas you
> appear interested in making an indexed assignment to a vector.
>
>
>>
>> Is it possible? If it isn't and I manually create each function then is
>> their a way to call them through a loop?  My objective is to calculate
>> something like
>>
>> result.k = ff.k(x1)/ff.k(x2)      for k in 2:n
>
>
> You may have clear idea about which k-indices should go where in that
> expression, but I surely do not. What are 'x1' and 'x2'?
>
> --
>
> David Winsemius, MD
> West Hartford, CT
>
>
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