having one "for" loop instead of two

Hello all,

I have two "for" loops.

for a=0:10
for b=0:10
c=a+b;
end
end

I would like two combine them and put them in one "for" loop but I have error.

for a=0:10 && b=0:10
c=a+b;
end

Can anybody help me? thanks.

[Daniel Shub]

This doesn't make any sense. You keep over writing c on every iteration.

[Walter Roberson]

You cannot iterate two variables in one "for"

Answer 1

[Jan]

Actually it is said already. But not explicitely:

a = 0:10;
b = 0:10;
for k = 1:length(a)
  c = a(k) + b(k);
end

[Bahareh]

Thanks Mr. Simon. Now if I want to have a surface plot using 'surfl' of 'c' versus 'a', and 'b' what should I do? Can you please help me?

[Daniel Shub]

See, now if you had asked this question from the outset, you would have had an answer by now ...

This is really a new question and should be asked as such.

[Matt Tearle]

This doesn't make sense, though. Your whole point was that you wanted to evaluate c at the same values of a and b, not at every combination of a and b. So you're not making a surface -- you're making a line (along the diagonal in a-b space). In other words, you don't have c(0,7) or c(3,2) or ..., which you need to make a surface. All you have is c(0,0), c(1,1), c(2,2), etc.

[Walter Roberson]

The new question that was created was http://www.mathworks.com/matlabcentral/answers/22579-surface-plot

I show how to embed the line within a surface there. It isn't a useful thing to do in this situation, but perhaps it will be useful for someone else.

Answer 2

[Matt Tearle]

As Walter said, you can't loop over two variables in the same for-loop. So the real question is: why do you want to do this? What's the problem with the two nested loops that you're trying to avoid/fix/solve?

[Bahareh]

In the two loop case, each value of a corresponds to 11 values of b. I wan each value of a be corresponding to one value of b; in other words, I wan a=0 be corresponding to b=0 and a=5 be corresponding to b=5?

Answer 3

[Hin Kwan Wong]

Your code does not make sense because it's overwriting c each time you loop it Your answer is just equal to c = last a + last b = 10+10 = 20

If you want to sum all c values: a=0:10; b=a; sum([a+b])

Answer 4

[Walter Roberson]

for a=0:10
  b = a;
  c = a + b;
end

Answer 5

[Michael]

From the comments I think you want the surface c = a + b

Just use a nested loop

c = zeros(11);
for a = 0:10
    for b = 0:10
        c(a+1,b+1) = a + b;
    end
end
surf(a,b,c)