error : Function integration trapezoidal
显示 更早的评论
i want to calculate area from numerical integration of function f(x) with the limits a to b and vary n . by the way i use this code from my handbook, numerical chapra. to solve my problem. but the result was error.
function I = trap(func,a,b,n,varargin)
% trap: composite trapezoidal rule quadrature
% I = trap(func,a,b,n,p1,p2,...):
% composite trapezoidal rule
% input:
% func = name of function to be integrated
% a, b = integration limits
% n = number of segments (default = 100)
% p1,p2,... = additional parameters used by func
% output:
% I = integral estimate
if nargin<3,error('at least 3 input arguments required'),end
if ~(b>a),error('upper bound must be greater than lower'),end
if nargin<4|isempty(n),n=100;end
x = a; h = (b - a)/n;
s=func(a,varargin{:});
for i = 1 : n-1
x = x + h;
s = s + 2*func(x,varargin{:});
end
s = s + func(b,varargin{:});
I = (b - a) * s/(2*n);
the error :
??? function I = trap(func,a,b,n,varargin)
|
Error: Function definitions are not permitted in this context.
what should i do ?
--- my purpose is to make the table like below this text, to known how the error result with vary n parameter.
%
采纳的回答
sixwwwwww
2013-12-4
0 个投票
Maybe following links are helpful for you for this purpose:
These links shows how to use matlab functions. and how to input and get output values from them
4 个评论
sixwwwwww
2013-12-4
'varargin' mean variable number of input arguments and 'nargin' mean number of input arguments. If you use 'varargin' in function definition then you can input any number of arguments to that function and by using 'nargin' you can know how many arguments are input to a function. For more information see:
Good luck!
Ahzabuddin
2016-5-20
can you help me too??? I get trapezoidal single... but I have trouble unequal trapezoidal.
x = [0 .12 .22 .32 .36 .4 .44 .54 .64 .7 .8];
y = 0.2+25*x-200*x.^2+675*x.^3-900*x.^4+400*x.^5;
>>trapuneq(x,y)
??? Undefined function or variable 'l'.
Error in ==> trapuneq at 18
s = s+(x(k+l)-x(k))*(y(k)+y(k+l))/2;
my formula M-File is
if nargin<2,error('at least 2 input arguments required'),end
if any(diff(x)<0),error('x not monotonically ascending'),end
n = length(x);
if length(y)~=n,error('x and y must be same length'); end
s = 0;
for k = 1:n-1
s = s+(x(k+l)-x(k))*(y(k)+y(k+l))/2;
end
I = s;
Sam
2023-4-14
Changing the 2 "l"s ("L"s; Capital shown for variable clarity) to a "1" ("One") in the line of the For loop fixes the error and allows the same anser to be attained as shown in the textbook (1.5948).
更多回答（1 个）
My guess is that the "l" in the formula
s = s+(x(k+l)-x(k))*(y(k)+y(k+l))/2;
should be a "1".
Best wishes
Torsten.
类别
在 帮助中心 和 File Exchange 中查找有关 Startup and Shutdown 的更多信息
Translated by 
