Question

我正在尝试调用数值积分函数（即使用梯形方法的函数）来计算定积分。但是，我想将多个'n'值传递给以下函数，

function I = traprule(f, a, b, n)

if ~isa(f, 'function_handle')
    error('Your first argument was not a function handle')
end

h = (b-a)./ n;
x = a:h:b; 
S = 0;
for j = 2:n
S = S + f(x(j));
end
I = (h/2)*(f(a) + 2*S + f(b)); %computes indefinite integral
end

我正在使用; f = @(x) 1/x，a = 1和b = 2。我也试图传递n = 10.^(1:10)，但是，当我这样做时，我得到I的以下输出，

I =

  Columns 1 through 3

   0.693771403175428   0.069377140317543   0.006937714031754

  Columns 4 through 6

   0.000693771403175   0.000069377140318   0.000006937714032

  Columns 7 through 9

   0.000000693771403   0.000000069377140   0.000000006937714

  Column 10

   0.000000000693771

关于如何使函数获取n = 10.^(1:10)的任何想法，所以我得到类似的输出，

I = 0.693771403175428,0.693153430481824,0.693147243059937 ......依此增加10的功率？

Answer 1

在您调用此脚本的脚本中，只需遍历n

即可

k = 3;
f = @(x)1./x;
a = 1; b = 2;
I = zeros(k,1);
for n = 1:k 
    I(n) = traprule(f, a, b, 10^n);
end

% output: I = 0.693771403175428
%             0.693153430481824
%             0.693147243059937

然后I将包含所有输出。或者，您可以调整函数以使用相同的逻辑来循环传递n的元素作为载体。

注意，您可以通过删除traprule循环来提高for代码的效率：

% This loop operates on every element of x individually, and is inefficient
S = 0;
for j = 2:n
    S = S + f(x(j));
end
% If you ensure you use element-wise equations like f=@(x)1./x instead of f=@(x)1/x
% Then you can use this alternative:
S = sum(f(x(2:n)));

试图获得一个MATLAB函数来获取一组输入

1 个答案: