[R] Simultaneous equations

[Berend Hasselman]

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 intended for estimating a system of simultaneous equations.
You seem to want to solve a system.
I assume you want to solve this system for x and y.

You could use package nleqslv as follows:

library(nleqslv)

fun <- function(x) {
     f <- numeric(length(x))
     f[1] <-  x[2] - 1/x[1]
     f[2] <-  x[2] - sin(x[1])
     f
}
x.start <- c(1,1)
nleqslv(x.start,fun)  # will give 1.1141571 0.8975395

x.start <- c(2,2)
nleqslv(x.start,fun)  # will give 2.7726047 0.3606717


Berend

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