error : Function integration trapezoidal

12 visualizzazioni (ultimi 30 giorni)
jakv
jakv il 3 Dic 2013
Commentato: Sam il 14 Apr 2023
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.
%
  2 Commenti
sixwwwwww
sixwwwwww il 3 Dic 2013
you can't directly run this function. first save it in an m-file with name 'trap.m' and then call with appropriate input parameters from command prompt or from another script
jakv
jakv il 3 Dic 2013
what the script that i can use ? sorry i'm newbie.

Accedi per commentare.

Risposta accettata

sixwwwwww
sixwwwwww il 4 Dic 2013
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 Commenti
Ahzabuddin
Ahzabuddin il 20 Mag 2016
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
Sam il 14 Apr 2023
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).

Accedi per commentare.

Più risposte (1)

Torsten
Torsten il 20 Mag 2016
Modificato: Torsten il 20 Mag 2016
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.

Categorie

Scopri di più su Loops and Conditional Statements in Help Center e File Exchange

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by