Hi, can anyone tell me what is the problem of this? It says "Operands to the || and && operators must be convertible to logical scalar values."

1 次查看(过去 30 天)
function [ x,niter ] = NewtonRaphson( x0,tol,nmax )
%DATA
N = 20;
niter = 0;
error = 1;
x0 = zeros(N-1,1);
dx = zeros(N-1,1);
while ((error > tol) && (niter < nmax))
niter = niter + 1;
x = x0 - ((F_springs(x0))./(J_springs(x0)));
x0 = x;
error = max(abs(x-F_springs(x0)));
end
for i = 2:N-2
dx(i) = x(i)-x(i-1);
end
end

采纳的回答

Walter Roberson
Walter Roberson 2017-12-17
x0 = zeros(N-1,1);
so x0 is a vector.
x = x0 - ((F_springs(x0))./(J_springs(x0)));
x0 = x;
with x0 being a vector, x will be a vector; and then you assign it to x0 so x0 will stay a vector.
error = max(abs(x-F_springs(x0)));
with x and x0 being vectors, error is going to be a vector.
while ((error > tol) && (niter < nmax))
error is a vector, so error > tol is a vector. You now have a vector on the left side of && . But the && operator is strictly for scalars, never for vectors. For vectors you would need to use the & operator, as in
while ((error > tol) & (niter < nmax))
As niter<nmax is a scalar, the effect of that would be to calculate (niter < nmax) and to "and" it with each element of (error > tol), giving a vector of results.
The definition of if or while with a vector is to consider the condition to be true only of all of the items in the vector are non-zero. This would be equivalent to
while all((error > tol) & (niter < nmax))
which would stop as soon as any location in error was not greater than tol.
You should re-think why you want x0 to be a vector. If you have a good reason for it being a vector, then think about whether you truly want the entire vector to be involved in the calculations each time.

更多回答(0 个)

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by