On 09/02/2010 09:25 PM, benhartley903 wrote:

>

> Dear all,

> I am relatively new to R and have had some difficulty in understanding the

> user manual for a package that I have downloaded to evaluate non-linear

> simultaneous equations.

> The package is called systemfit.

> Does anyone have any experience of this package?

> What I am trying to do is solve a non linear simultaneous equations...

>

> Could anyone give me an example (please) of the code that would be needed to

> return solutions for the following system using systemfit (or any other

> better package):

>

> y=1/x

> y=sin(x)

>

> within a range of say x=-10 to 10 (x in radians)

>

> Thanks, I really appreciate your help in advance.

>

> Ben

Systemfit is not even in the same ballpark...!

I'd just rewrite the above as

x * sin(x) - 1 = 0

make a graph to bracket the roots and then use uniroot.

> f <- function(x) x*sin(x)-1

> curve(f, interval=c(-10.10)

> f(c(0,2,5,7,10))

[1] -1.0000000 0.8185949 -5.7946214 3.5989062 -6.4402111

So the roots are

> uniroot(f,interval=c(7,10))$root

[1] 9.317241

> uniroot(f,interval=c(5,7))$root

[1] 6.43914

> uniroot(f,interval=c(2,5))$root

[1] 2.772631

> uniroot(f,interval=c(0,2))$root

[1] 1.114161

and 4 more symmetrically below zero.

--

Peter Dalgaard

Center for Statistics, Copenhagen Business School

Phone: (+45)38153501

Email:

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