Santi,
In the second line of your function you have the following:
f <- numeric(length(x))
This sets the length of this numeric vector (i.e., "f") to the length of the
vector "x".
Later, inside the function you assign to values to 4 elements of the vector "f".
This assumes that "f" is at least 4 element in length.
However, you define "startx" to be a numeric vector of length 2 with
startx <- c(16350, 1.33)
which you then use as the argument to the function "fun" (bad name for a
function, by the way, as it is not descriptive).
Thus, when "x" inside your function gets the value of "startx" it becomes a
numeric vector of length 2, which is then used to set the length of the numeric
vector "f". As soon as the function tries to assign a value to f[3], R
correctly throws an informative error.
Mark
R. Mark Sharp, Ph.D.
msh...@txbiomed.org
> On Aug 9, 2017, at 3:56 PM, Santi Burone <santiagobur...@gmail.com> wrote:
>
> Dear all,
> I am relatively new to R and have had some difficulty in understanding an
> error i get when running a code to solve a system of non-linear equations,
> with four equations and two variables.
>
> This is my code:
>
> ALPHA <- c(-0.0985168033402, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4)
> BETA <- c(-0.0985168033402, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4)
> GAMMA <- c(0.3940672148378, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4)
> MEA <- 30000
> MIA <- 10000
> MAA <- 50000
> DEA <- 0.385
> fun <- function(x) {
> f <- numeric(length(x))
> f[1] <- 1*x[1] -
> ((((MEA*((0.5*((MIA-MEA)^2))^(-BETA[1+j]))*((0.5*((MAA-MEA)^2))^(-ALPHA[1+i]))*((DEA)^(-GAMMA[1+k]))))*((12^0.5)^(-GAMMA[1+k])))/(((0.5)^(-BETA[1+j]-ALPHA[1+i]))*(((1-1*x[2])/(2))^(-BETA[1+j]))*(((-1+1*x[2])/(2))^(-ALPHA[1+i]))*(2*(1*x[2]-1)^(-GAMMA[1+k]))))^(1/(-1-BETA[1+j]-ALPHA[1+i]-1.5*GAMMA[1+k]))
> f[2] <- 1*x[1] -
> (((MAA*((0.5*((MIA+MAA)^(2)))^(-BETA[1+j]))*((DEA)^(-GAMMA[1+k])))*((12^0.5)^(-GAMMA[1+k])))/((1*x[2])*(2^(-BETA[1+j]-GAMMA[1+k]))*((1*x[2]-1)^(-GAMMA[1+k]))*((((1-1*x[2])^2)/2)^(-BETA[1+j]))))^(1/(1-2*BETA[1+j]-1.5*(GAMMA[1+k])))
> f[3] <- 1*x[1] -
> (((MIA*((0.5*((MIA+MAA)^(2)))^(-ALPHA[1+i]))*((DEA)^(-GAMMA[1+k])))*((12^0.5)^(-GAMMA[1+k])))/((2-1*x[2])*(2^(-ALPHA[1+i]-GAMMA[1+k]))*((1*x[2]-1)^(-GAMMA[1+k]))*((((-1+1*x[2])^2)/2)^(-ALPHA[1+i]))))^(1/(1-2*ALPHA[1+i]-1.5*(GAMMA[1+k])))
> f[4] <- 1*x[2] > 1
> f
>
> }
>
> Result <- matrix(0,nrow=9*9*9,ncol=6)
> startx<-c(16350, 1.33)
> indx <- 1
> for (i in 1:9) {
> for (j in 1:9) {
> for (k in 1:9) {
> f.startx <- fun(startx)
> if(anyNA(f.startx)) {
> Result[indx,1:3] <- NA
> } else {
> z <- nleqslv(startx,fun)
> Result[indx,1:3] <- c(z$termcd,z$x)
> }
> Result[indx,4:6] <- c(i,j,k)
> indx <- indx+1
> }
> }
> }
>
>
> The error i get when solving for specific values of ALPHA, BETA and GAMMA,
> not using the loop is:
>
> Error in nleqslv(xstart, fun) : Length of fn result <> length of x!
>
> I had already solved this problem useing ALPHA, BETA and GAMMA as X[1], X[2]
> and X[3] and being X[1] and X[2] of this system given values, in that case
> for the first values of alpha beta and gamma given here the solution was
> (16350, 1.33).
> I dont understand what’s the error i get here, as i know the system as a
> unique solution. "What’s the meaning of Length of fn result <> length of x!"?
>
> Thanks in advance!
> Santiago.
> [[alternative HTML version deleted]]
>
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