# [R] help about solving two equations

Shaoqiong Zhao zhaos at uwm.edu
Fri Mar 12 03:00:55 CET 2010

```Hello Professor Ravi,

I tried to load BB into R, but I got the following message:
library("BB")
Error in library("BB") : there is no package called 'BB'
> library(BB)
Error in library(BB) : there is no package called 'BB'

Can you tell me why?

Thanks a lot.

Annie

----- Original Message -----
To: "Shaoqiong Zhao" <zhaos at uwm.edu>
Cc: r-help at r-project.org
Sent: Wednesday, March 10, 2010 9:03:25 PM GMT -06:00 US/Canada Central
Subject: Re: [R] help about solving two equations

Here is how you can solve:

fn <- function(x, s){
f <- rep(NA, length(x))
f <- digamma(x) - digamma(x+x) - s
f <- digamma(x) - digamma(x+x) - s
f
}

require(BB) # load this package for the nonlinear solver

s <- c(-2, -4)  # one row of s1 and s2

ans <- dfsane(par=c(1,1), fn=fn, s=s)

ans\$par  # solutions for p and q

You can then loop through for each row of s1 and s2 and solve it to get corresponding p and q.

Ravi.
____________________________________________________________________

Assistant Professor,
Division of Geriatric Medicine and Gerontology
School of Medicine
Johns Hopkins University

Ph. (410) 502-2619

----- Original Message -----
From: Shaoqiong Zhao <zhaos at uwm.edu>
Date: Wednesday, March 10, 2010 8:19 pm
Subject: [R] help about solving two equations
To: r-help at r-project.org

> I have two matrix s1 and s2, each of them is 1000*1.
>  and I have two equations:
>  digamma(p)-digamma(p+q)=s1,
>  digamma(q)-digamma(p+q)=s2,
>  and I want to sovle these two equations to get the value of x and y,
> which are also two 1000*1 matrices.
>
>  I write a program like this:
>
>  f <- function(x) {
>  p<- x; q <- x;
>   ((digamma(p)-digamma(p+q)-s1[2,]) )^2
> +((digamma(q)-digamma(p+q)-s2[2,]) )^2
>   }
>  s <- 1:10/10
>  g <- expand.grid(p = s, q = s)
>  idx <- which.min(apply(g, 1, f))
>  idx
>  g[idx,]
>
>  I am not sure if this is correct and also this can only solve one
> row. How to get the whole 1000 rows of p and q?
>
>  Thanks.
>
>  Annie
>
>  ______________________________________________
>  R-help at r-project.org mailing list
>