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目前我正在对 Secant Method 编写代码,到目前为止代码运行正常。但是,我仍然需要通过计算我在“割线”函数中使用的函数调用次数来更新我的“count.funcCount”。我应该如何修改我的代码?

这是我到目前为止的代码:

function [ root, fcneval, count ] = secant(f, x0, x1, my_options)
my_options = optimset('MaxIter', 50, 'TolFun', 1.0e-5);
count = struct('iterations',0,'funcCount',0,'message',{'empty'});
xp = x0; %# Initialize xp and xc to match with
xc = x1; %# x0 and x1, respectively
MaxIter = 100;
TolFun = 1.0e-5;

%# Secant Method Loop
for i = 2:MaxIter 
    fd = f(xc) - f(xp); %# Together, the ratio of d and fd yields
    d = xc - xp; %# the slope of the secant line going through xc and xp
     xn = ((xc * fd) - (f(xc) * d)) / fd; %# Secant Method step

    if (abs(xc - xn) < TolFun) && (abs(f(xn)) < TolFun) %# Stopping condition
        break;
    elseif i > MaxIter  %# If still can't find a root after maximum
                        %# 100 iterations, consider not converge
        count.message = sprintf('Do not converge');
    end

    xp = xc; % Update variables xc and xp
    xc = xn;
end 

%# Get outputs:
root = xn;
fcneval = f(root);
count.iterations = i;
end %# end function

---------------------------------------
function [f] = fun(x)
f = cos(x) + x;
end

请帮助我,提前谢谢你

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2 回答 2

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虽然我不明白你的问题,但我仍然认为你可以使用计数器。将其初始化为零并在每次调用函数时递增。您正在使用内置函数,只需对其源代码进行必要的更改(仅供参考:您可以在 matlab 中执行此操作)然后用新名称保存它,然后在您的主代码中使用它。

于 2012-07-11T07:44:32.927 回答
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您可以创建一个嵌套函数,该函数可以访问其父函数的变量(包括函数f和计数器count.funcCount)。该函数将调用执行计算的实际方法,然后递增计数器。

这是一个相当愚蠢的例子来说明这个概念:

function [output,count] = myAlgorithm(f, x0)
    count = 0;
    output = x0;
    while rand()<0.99         %# simulate a long loop
        output = output + fcn(x0);
    end

    %# nested function with closure
    function y = fcn(x)
        %# access `f` and `count` inside the parent function
        y = f(x);             %# call the function
        count = count + 1;    %# increment counter
    end
end

现在您将其称为:

[output,count] = myAlgorithm(@(x)cos(x)+x, 1)
于 2012-07-11T15:34:34.980 回答