evaluating elements of a vector in a function file

Hi, guys, I am not much of an experienced programmer ,this might sound stupid but I am having trouble with a code below .I want to use each element of my input vector taken in by the function I created. I want to use each element and whatever answers I get from the evaluation of each element, I want it to be stored in a vector that I wish to return to where the function was called , however, it seems like the forloop is not working well as it stops after evaluating one element . what am I doing wrong ?

function [ M ] = new_vector(x)

%This function takes in vector containing various x values
%The the sum of M(1,2,3..) is evaluated at that specific x and the value is appended to the matrix M 

M = zeros(1,6);

for i = 1:6

      M1 = RA*(x(1,i));
      sum_of_Ms = 0+M1;

      M2 = RB*(x(1,i)-5);
      if M2 <= 0
          break
      else
        sum_of_Ms = sum1+M2;
      end

      M3 = -w*(x(1,i)-7.5);
      if M3 <= 0
          break
      else
          sum_of_Ms = sum_of_Ms+M3;
      end

      M4 = RC*(x(1,i)-10);
      if M4 <= 0
          break
      else
          sum_of_Ms = sum_of_Ms+M4;
      end

      M5 = RD*(x(1,i)-15);
      if M2 <= 0
          break
      else
          sum_of_Ms = sum_of_Ms+M5;
      end

      M6 = RE*(x(1,i)-20);
      if M6 <= 0
          break
      else
         sum_of_Ms = sum_of_Ms+M6;
      end
      M(1,i)= sum_of_Ms
  end
  end

Answer 1

[Guillaume]

See comments to Massimo's answer about break.

I suspect what you meant to do is not add M? to the sum if it's negative, in which case you simply do nothing in the if statement:

if M1 <= 0
else
   sum_of_Ms = sum_of_Ms + M1;
end

but even better, you simply invert the logical test and don't bother with else:

if M1 > 0
   sum_of_Ms = sum_of_Ms + M1;
end

The above should be enough for you to fix your code, but you actually don't need any of the if. The following is a much better way of doing what you want in matlab:

M = zeros(size(x));  %I assume M must be the same length as x, in which case don't hardcode the size, just query it.
for i = 1:numel(x)   %again don't hardcode sizes
    subM = [RA * x(i), ...  %1D indexing makes more sense for vector
            RB * (x(i) - 5), ...
            -w * (x(i) - 7.5), ...
            RC * (x(i) - 10), ...
            RD * (x(i) - 15), ...
            RE * (x(i) - 20)];  %put all your M? into one vector
    M(i) = sum(subM(subM > 0)); %and only sum those values that are positive
end

[ANOZ21]

@Guillaume, As I said I am still a beginner at this, but I actually realised after a while that the break was the main problem. Thank you so much for your help ,that solved my problem and my code is working now . I like the last solution , it's very elegant and short. Thanks a lot :)

Answer 2

[Massimo Zanetti]

First, the "for" loop stop at first iteration because it enters in one "break" condition. Second, in order to fix it, please give an explanation of what your algorithm should do with such vector x, then I can try to help you do the work. What kind of vector is x? What are RA,RB,RD?

[Guillaume]

@ANOZ21, yes, it is clear that you don't know what break does as none of them make any sense in your code as it is.

break immediately stops the for loop and jumps to just after its end. Since there's nothing after that in your code, in effect break ends the function. As you only assign values other than zero to the output at the end of the loop, you're returning a vector of 0 as soon as you hit a break.

It looks like you hit a break at the first if since otherwise you'd be executing the

else
      sum_of_Ms = sum1+M2;

which would result in an error since sum1 is not defined.

[ANOZ21]

@ Massimo Zanetti the problem is solved as I said below the 'break' was the main issue...so my problem is solved now ,but in future I'll make sure I include an explanation of the algorithm. Thanks for your willingness to help .