From vector to a step function

f.main <- function(vec){

f1 <- f.main(c(3,4,5,1,2,3,4,5))
f2 <- f.main(c(5,6,2,4,7,3,2,5))
f3 <- f.main(c(1,2,4,7,3,1,3,5))

f1(c(-2.5,-2,-.5,0,.5,1.5,2.5))

f2(c(-2.5,-2,-.5,0,.5,1.5,2.5))

f3(c(-2.5,-2,-.5,0,.5,1.5,2.5))

Greetings R members.

I have a few vectors that denote the 'steps' of different step functions
v1=c(3,4,5,1,2,3,4,5)
v2=c(5,6,2,4,7,3,2,5)
v3=c(1,2,4,7,3,1,3,5)

Here v1,v2,v3 are considered as the steps for the f1,f2,f3 step functions.

For example f1 looks like that (step size is always same and fixed)

f1= 3 (x>=-3,x<-2)
f1= 4 (x>=-2,x<-1)
f1= 5 (x>=-1,x<0)
f1= 1 (x>=0, x<1)
and so on.

What I only have are these vectors that are interpreted as functions (as shown above, x (step is 1 here). I would like to ask your help of how I can create some function that reads one of the vector v1,v2,v3.... and returns results that are acceptable by integrate() function.

Usually integrate wants a pre-defined function like
myfunc(x)<-function{ x^2 }
but this is not the case here.

Could you please give me some hints how I can proceed?

I would like to thank u in advance for your help

Regards
Alex

From: jim holtman <jholtman at gmail.com>
Subject: Re: [R] From vector to a step function
To: "Alaios" <alaios at yahoo.com>
Cc: r-help at r-project.org
Date: Monday, January 10, 2011, 5:44 PM
try this:

f.main <- function(vec){

+? ???breaks <- seq(-3, by = 1,
length = length(vec) + 1L)
+? ???function(x){
+? ? ? ???indx <-
findInterval(x, breaks)
+? ? ? ???vec[indx]
+? ???}
+ }

f1 <- f.main(c(3,4,5,1,2,3,4,5))
f2 <- f.main(c(5,6,2,4,7,3,2,5))
f3 <- f.main(c(1,2,4,7,3,1,3,5))

f1(c(-2.5,-2,-.5,0,.5,1.5,2.5))

[1] 3 4 5 1 1 2 3

f2(c(-2.5,-2,-.5,0,.5,1.5,2.5))

[1] 5 6 2 4 4 7 3

f3(c(-2.5,-2,-.5,0,.5,1.5,2.5))

[1] 1 2 4 7 7 3 1

On Mon, Jan 10, 2011 at 11:42 AM, Alaios <alaios at yahoo.com>
wrote:

Greetings R members.

I have a few vectors that denote the 'steps' of

different step functions

v1=c(3,4,5,1,2,3,4,5)
v2=c(5,6,2,4,7,3,2,5)
v3=c(1,2,4,7,3,1,3,5)

Here v1,v2,v3 are considered as the steps for the

f1,f2,f3 step functions.

For example f1 looks like that (step size is always

same and fixed)

f1= 3 (x>=-3,x<-2)
f1= 4 (x>=-2,x<-1)
f1= 5 (x>=-1,x<0)
f1= 1 (x>=0, x<1)
and so on.

What I only have are these vectors that are

interpreted as functions (as shown above, x (step is 1
here). I would like to ask your help of how I can create
some function that reads one of the vector v1,v2,v3.... and
returns results that are acceptable by integrate()
function.

Usually integrate wants a pre-defined function like
myfunc(x)<-function{ x^2 }
but this is not the case here.

Could you please give me some hints how I can

proceed?

I would like to thank u in advance for your help

Regards
Alex

mailing list

reproducible code.

-- 
Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?

x

str(x)

x<-legendre.polynomials(2)[[3]]

x

-0.5 + 1.5*x^2

str(x)

Class 'polynomial'  num [1:3] -0.5 0 1.5

As you can see from the code above str(x) returns that x is of class
polynomial. I want to use that polynomial as a function. The reason for
that is that I would be grateful if I can feed that kind of function
inside integrate(f,lower=,upper=)