• function IntegralCalculator

  func= input('Enter an equation in x: ','s') ;

  f = str2func(['@(x) ' func]);

  a= input('Enter the bottom limit of the integral: ');

  b= input('Enter the upper limit of the integral: ');

  n = input('Enter the number of nodes for the integral: ');

  method = input('Enter the method you want to use in capital letters: ', 's');

  int=0;

  while strcmp('LA',method)

  dx=(b-a)/n;

  r=f(a);

  for i = 1:n-1

  c=a+i*dx;

  r=r+f(c);

  end

  r=dx*r;

  nv=r;

  err= (nv-r)/nv;

  disp(["Your Left side estimate is",num2str(r)])

  disp(["Your approximated error is",num2str(err)])

  plot(1:n, r, '-', 'LineWidth', 2,'Color', 'b');

  return

  end

  while strcmp('RA', method)

  dx=(b-a)/n;

  w=f(a);

  for i = 1:n+1

  c=a+i*dx;

  w=w+f(c);

  end w=dx*w;

  disp(["Your Right side estimate is",num2str(w)])

  return

  end

  while strcmp('TR', method)

  d = linspace(a,b,n+1);

  v =d(2)-d(1);

  ls = sum(f(d(1:n))*v);

  rs = sum(f(d(2:n+1))*v);

  te = (ls +rs)/2;

  disp(["Your Trapezoidal estimate is",num2str(te)])

  return

  end

  while strcmp('MR', method)

  dx =(b-a)/n;

  for i= a:dx:b

  int = int + f(i+dx/2);

  end

  in =dx* int;

  disp (['Your Mid point estimate is: ', num2str(in)])

  return

  end

  while strcmp('3FD', method)

  dx =(b-a)/n;

  o=0;

  e=0;

  if rem(n,2)==1

  disp('ERROR! Enter a valid n')

  input("Enter n as an even number ")

  end

  for i =1:1:n-1

  s=f(a+(i*dx));

  o =o + f(s);

  end

  for i = 2:2:n-2

  s=f(a+(i*dx));

  e=e+f(s);

  end

  int = (dx/3) .* ((f(a)+f(b))+4 .*o + 2.*e);

  disp (['Your Simpson point estimate is: ', num2str(int)])

  return

  end

  end

  This is the code that I have. It is to use 5 different ways to approximate the calculation of an integral. It is working to do the approximations that I need to do. However, I need to calculate the error between the exact value and the approximation and plot the graph. I tried different things, but I haven't been able to get it to give me the error or the graph. I do not know what the function will be or the bounds for it because they have to be inputted by the user, so I do not have that information at the beginning. This is the last attempt that I tried but it did not work neither.