I have a nonlinear algebraic equation representing the relationship between the stress strain of concrete. I need to calculate the modulus of concrete at every point on the curve. How can I get iteration of converged solution using Matlab to get the real value of concrete modulus.
Matlab's fsolve function is meant specifically for solving nonlinear algebraic equations. However, it requires initial guess. Is there any reason to suspect that this system of equations has more than one solution? If so, you'll need to provide a reasonably accurate initial guess. A good choice for x0 is a simplified version of your original problem (especially a simplified linear problem of the form Ax = b for which exact solution is possible.)
The stability of fsolve can be significantly improved by providing an analytic expression for the Jacobian matrix and using the trust-region-reflective algorithm. You'll have to decide if this problem justifies the extra labor of writing the Jacobian (though the symbolic math toolbox is quite helpful for this). Read further on that here: http://www.mathworks.com/help/optim/ug/nonlinear-equations-with-jacobian.html?refresh=true
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