Numeric integration with Trapezoidal and Simpson's rule

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Jhonie Habimana 2020-11-25

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/662023-numeric-integration-with-trapezoidal-and-simpson-s-rule

评论： Jon 2020-11-25

I am trying to write a code that allows a user pick between Trapezodal and simpsons method of integration and then after picking the code will let the integrate a given formula 𝑦 = 𝑥 −1 + √𝑥𝑒 ^x . My code is not running however and i was wondering where I may be going wrong

clc

clear

%Lower limit (a)

a = input('What is your lower limit (a)? \n');

% Upper limit (b)

b = input('What is your upper bound (b)? \n');

% Subintervals, it is an even number

N = input('How many subintervals (N)? \n');

%y=1./x+ sqrt(x).*exp(x);

% Calculating the integral

clear

clc

function s=simprl(f,a,b,N)

h=(b-a)/N;

s1=0;

s2=0;

for i=1:N

x=a+h*(2*i-1);

s1=s1+f(x);

end

for i=1:(N-1)

x=a+h*2*i;

s2=s2+f(x);

end

s=h*(f(a)+f(b)+4*s1+2*s2)/3; %composite simpsons formula without error

fprintf('s =%f\n',simprl)

end

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VBBV 2020-11-25

Is f a function ? or vector ? it seems you are trying to pass function as argument to a function

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Answer 1

Jon 2020-11-25

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https://ww2.mathworks.cn/matlabcentral/answers/662023-numeric-integration-with-trapezoidal-and-simpson-s-rule#answer_555883

在 MATLAB Online 中打开

You may have other problems too, but it looks like you clear all of your variables right after you just defined your limits and number of subintervals. You should not have the lines of code

% Calculating the integral
clear
clc

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Jhonie Habimana 2020-11-25

Thank you so much I will implement this immediately, how do I call a function

Jon 2020-11-25

在 MATLAB Online 中打开

In general if you have a function, lets call it myfun with for example arguments a,b,c that returns one argument then somewhere in your code you would just use for example

% just an illustrative example
a = 2
b =26.3
c = 15
y = myfun(a,b,c)

In your case it is a little more complicated because the first argument to your function is a function. (the integrand) You need to pass a handle to that function. See https://www.mathworks.com/help/matlab/matlab_prog/pass-a-function-to-another-function.htmlHere's one way to do it

% assuming a,b, and N are defined earlier in your code, then use
f = @(x) 1./x+ sqrt(x).*exp(x);
y = simprl(f,a,b,N)

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Numeric integration with Trapezoidal and Simpson's rule

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Numeric integration with Trapezoidal and Simpson's rule

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