Thanks. the approxfun command works great --matches exactly with computing each point-to-point slope
Eric
----- Original Message -----
From: jim holtman
To: Eric C. Jennings
Cc: R-help
Sent: Saturday, February 25, 2006 9:27 PM
Subject: Re: [R] how to get f(x)=___ from a piecwise function
?approxfun
> x<- c(-100.4, 32.0, 99.8, 200.2, 300.6, 399.8, 500.0, 600.0, 699.6, 799.6,
+ 899.8)
> y<- c(0.4, 0.0, 0.2, -0.2, -0.6, 0.2, 0.0, 0.0, 0.4, 0.4, 0.2)
> x.f <- approxfun(x,y)
> x.f(356)
[1] -0.1532258
On 2/25/06, Eric C. Jennings wrote:
>From actual real-world readings, I have two vectors:
x<- c(-100.4, 32.0, 99.8, 200.2, 300.6, 399.8, 500.0, 600.0, 699.6, 799.6,
899.8)
y<- c(0.4, 0.0, 0.2, -0.2, -0.6, 0.2, 0.0, 0.0, 0.4, 0.4, 0.2)
which, in the usual way constitute a continuous piecewise function.
What I want to do is find an easy method to get at f(x) for some x I have
NOT specified in the above vector. For example I want f(356).
I have already put the time and effort in to write a program to compute this
by breaking the function into the various pieces and computing the slopes of
the individual lines etc. etc.
I am just looking to find an easier method.
Thank you for your help.
Eric
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Jim Holtman
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What the problem you are trying to solve?
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