MATLAB: I dont know how to script this operation.

homeworkmatlab basics

function s = sumUp(X)
%Simple function in MATLAB.
%   s=sumUp(x) is a function that returns s given s=Sigma(X(i)).
% Caution! X here is a vector: X=[ x1 x2 ... xn].
s = 0;
% ============= YOUR CODE HERE ==============
% Instructions: Return s given s=Sigma(X(i)), X is a vector.
%               Use built-in function length(X) to obtain the length of X.
%               Use for loop to sum up all elements of X.
% ===========================================
end

Best Answer

Try the following code.

function s = sumUp(X)
   s = 0;
   for s=1:length(X)
      s = s + X(s);
   end
end

Related Solutions

MATLAB: Summing elements of any vector using a for loop

No need for both adder and S. Simply have this:

function S = mySum(X)
% MYSUM  Sum of elements
% S = mySum(X) is the sum of the elements of the vector or array X.
% Works for X of any number of dimensions and sizes.
S = 0;
for k = 1 : numel(X)
  S = S + X(k);  
end

MATLAB: Newton’s Method for nonlinear system vector operation.

Lechen - if I run through your code, I observe the following error

 Error using  + 
 Matrix dimensions must agree.
 Error in newton.m
        y = x + d;

because x is a 1x2 matrix and d is a 2x1 matrix. The simplest fix for this is to just change the input x from a 1x2 matrix to one that is 2x1

 a = newton(@F, @J, [1;1])

That will fix the error message. Now look closer at the newton function

 function y = newton(f,j,x) 
      step = 1;
      finalstep = 10;
      y = zeros (2,1);
      while step < finalstep
          d = j(x)\(-f(x));
          y = x + d;
          disp(y);
          x = y;
      end
 end

Note how the code does not increment the step local variable, so the code will become stuck in an infinite loop. Add a line to increment this variable. Also, consider adding it a line of code that compares x and y - if the difference between the two vectors (for each element) is less than some tolerance, then assume that no better solution will be found and so break out of the loop. The above then becomes something like

 function y = newton(f,j,x) 
      step = 1;
      finalstep = 10;
      y   = zeros (2,1);
      tol = 1e-5; 
      while step < finalstep
          d = j(x)\(-f(x));
          y = x + d;
          disp(y);
          % increment step
          step = step + 1;
          % compare each element of x and y
          exitEarly = true;
          for k=1:length(x)
              if abs(x(k)-y(k))>tol
                  % pair k exceeds tolerance so do not exit
                  % early
                  exitEarly=false;
              end
          end
          if exitEarly
              break;
          end          
          x = y;
      end
 end

Try the above and see what happens!

Best Answer

Related Solutions

MATLAB: Summing elements of any vector using a for loop

MATLAB: Newton’s Method for nonlinear system vector operation.

Related Question