Not enough inputs with input parser

Question

Ian Ammerman 2023-9-21

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2024137-not-enough-inputs-with-input-parser

编辑： Chunru 2023-9-22

I am trying to use input parser to add optional inputs to my own function, newtonsMethod:

function x = newtonsMethod(func,guess)
% newtonsMethod(func,guess) computes the zero of the function func using Newton's method
% beginning at the x = guess. If multiple solutions are known to be present near guess,
% consider using findZero instead.
%
% newtonsMethod(func,guess,tol) allows the user to specify the tolerance for
% convergence
%
% newtonsMethod(func,guess,tol,dx) specifies the increment dx used for
% computing the numerical derivative of func at a point.
p = inputParser;
addRequired(p,'func')
addRequired(p,'guess')
addOptional(p,'tol',10^-6)
addOptional(p,'dx',10^-4)
parse(p);
%% ---------------------------------------------------------------------- %%
maxiter = 10^7;
iter = 0;
x = guess;
while abs(func(x)) > tol && iter < maxiter
    fpx = (func(x+dx)-fx)/dx;
    x = x - fx/fpx;
end

I am then calling this function using a driver file:

F = @(x) x.^2.*sin(x)-0.2.*x.^3+3.*x.^2+x-4-0.005.*x.^4;
nx = newtonsMethod(F,6.5)

But I am getting the error "Not enough input arguments.". Adding tol and dx to the function definition yields the same error, as does adding varargin to the function definition and adding it to the parse command as parse(p,varargin{:}). My code seems to follow the Matlab documentation example directly but I can't seem to get it to run.

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Answer 1

Chunru 2023-9-22

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2024137-not-enough-inputs-with-input-parser#answer_1315592

编辑：Chunru 2023-9-22

在 MATLAB Online 中打开

F = @(x) x.^2.*sin(x)-0.2.*x.^3+3.*x.^2+x-4-0.005.*x.^4;
nx = newtonsMethod(F,6.5)
nx = -1.5544
function x = newtonsMethod(func,guess,tol,dx)
arguments
    func
    guess (1, 1) double
    tol   (1, 1) double = 1e-6;
    dx    (1, 1) double = 1e-4;
end
%% ---------------------------------------------------------------------- %%
maxiter = 10^5;
iter = 0;
x = guess;
fx = func(x);
while abs(fx) > tol && iter < maxiter
    fpx = (func(x+dx)-fx)/dx;
    x = x - fx/fpx;
    fx = func(x);
    iter = iter+1;   
end
end