how to find the error of a 2 column data set using repeated simpsons rule in matlab

To find the error of a 2-column data set using repeated Simpson's rule in Matlab, you can use the following code:

main.m
% First, load your data set into 2 arrays, x and y
x = [1 2 3 4 5]; % example x array
y = [2 4 1 3 5]; % example y array

% Next, set up the initial parameters for the repeated Simpson's rule
a = x(1); % lower bound of integration
b = x(end); % upper bound of integration
n = length(x) - 1; % number of sub-intervals
h = (b - a) / (2 * n); % step size

% Repeat Simpson's rule to calculate the approximate integral value
approx = y(1) + y(end); % initialize approximate value
for i = 1:n
    approx = approx + 4 * y(2*i - 1) + 2 * y(2*i); % add odd and even terms
end
approx = approx * h / 3;

% Finally, calculate the error using the composite Simpson's rule error formula
error = ((b - a) / 180) * h^4 * max(abs(diff(y))) % using the first derivative of y for max value
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This code uses the composite Simpson's rule error formula, which gives an approximation of the error as:

main.m
error = (b - a) / 180 * h^4 * max|f''(x)|,
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where f(x) is the function being integrated (in this case, y), and h is the step size used in the repeated Simpson's rule. The diff function is used here to calculate the first derivative of y, which is used to find the maximum value of f''(x) over the interval [a, b].

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