I don't know how to call my function

function norm = myvectornorm(x)

% calculate the norm
s=0;
n=length(x);
for i=1:length(x)
    s =s+ x*(i)^2;
end
norm= sqrt(s);


end

Answer 1

[John D'Errico]

What language are you using here? Possibly not MATLAB. :)

s = s + L*(i)^2;

Do you think that squares the number i, and then multiplies the square of that value by the vector L? After all, * tells MATLAB to multiply two things.

Or, did you want to access the i'th element of L, and then square it? But L is itself only the length of the vector x, so just the number of elements in x.

Or, do you relly want to access the i'th element of the vector x, square THAT, and then sum the result into s?

The code you wrote will not achieve the latter. For that to happen, you would need to write this:

s = s + x(i)^2;

[Joshua Vuong]

I'm trying but I want to find the vector norm by having a vecter be intputed and squaring each of those then adding them together and taking the squareroot. I tried both of the things you've said but I'm not getting anything.

[John D'Errico]

Seriously? Hmm. Let me try it.

Your function as I suggested it should be modified is below. Now, let me try it.

format long g
X = rand(1,5)

X = 1×5

0.52130891361818 0.381271730961512 0.521964614295369 0.18545668573984 0.959581648315824

norm(X) % this is the MATLAB 2-norm code. We know it is correct.

ans = 
          1.28248559325038

myvectornorm(X)

ans = 
          1.28248559325038

Here is the fixed code. There is only the one line that is different in what I changed.

function norm = myvectornorm(x)
% calculate the norm
s=0;
L=length(x);
for i=1:L
    s = s + x(i)^2;
end
normvalue=sqrt(s);
norm=normvalue;
end

It works with no problems at all. In fact, you were pretty close, except for that offending line of code. The rest was perfect.

Ok, not really perfect. It is a bad idea to name a variable norm. That will cause problems one day when you want to use the FUNCTION norm. But this is not a fatal error, just a dangerous thing to do.

So, I don't think you really did try what I suggested. Well, you apparently tried something. But god only knows what. :)

[Joshua Vuong]

Well thanks I appreciate it but as I said in the title I don't know how to call my function its for an assignment asking me to do multiplt tests for different vecotrs one being [1 1 1] another [ 1/sqrt(2) 0 1/sqrt(2)] I might have communicated my complications incorrectly my code works fine. This is for matlab grader and I would appreciate the help with out the snide comments. thanks

[Image Analyst]

Call it like this

x = [1,1,1]; % Whatever values you want.
norm = myvectornorm(x)