Re: [R] Does inverse function exist

From: Prof Brian Ripley <ripley_at_stats.ox.ac.uk>
Date: Sat 27 Jan 2007 - 13:44:10 GMT

Inverting a linear function is easy, and more generally functions need not be invertible. But uniroot() is very helpful in finding an inverse of a monotonic function, and the idea is used in some of the qxxxxx functions.

On Fri, 26 Jan 2007, phwang2000@ucla.edu wrote:

> Hi,
>
> I wrote a simple derivative program
>
> (ftest=deriv(y~x^2, c("x"), function(x){} ))
>
> I put (ftest=deriv(y~x^2, c("x"), function(x){} ))(1) which return 2
> which is correct.
>
> however, if I want the output to be 0 and hopefully a new inverse
> function can take in output (2) and return x=1. Can this be
> accomplished. Maybe output(0) can return x=0
>
> Thanks
> pat
>
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-- 
Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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Received on Sun Jan 28 00:58:17 2007

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