adding strings per component

Hi,

I have the following code:

for n = 1:4
      velocity = ['v_',num2str(n),' = n*2'];
      eval(velocity)
      position = ['x_', num2str(n), '= n.^2'];
      eval(position)
end

So, the expected output would be: v_1 = 2, x_1 = 1 \\ v_2 = 4, x_2 = 4 \\ … \\ v_4 = 8, x_4 = 16.

Let's say we want to do something to the components. For example, add v_1 + x_1, (we want to do something to variables with the same index.) How do we do that?

Answer 1

[Azzi Abdelmalek]

This is not a good idea, read this http://matlab.wikia.com/wiki/FAQ#How_can_I_create_variables_A1.2C_A2.2C....2CA10_in_a_loop.3F

[cgo]

Hello, I am lost. Please elaborate. What could be a better alternative/solution to the problem above?

Thanks

[Azzi Abdelmalek]

The alternative is to work with arrays, or cell arrays. In your case:

s(:,1)=(1:4)'*2
s(:,2)=(1:4)'.^2

The first column represent the velocity and the second represent the position. Why to create a name for each value when you can use just one? Then if you want to sum velocity and position

out=sum(s,2)

[cgo]

This is neater and elegant. Thank you.

[per isakson]

... or two structures called, e.g.&nbsp velocitiy &nbspand&nbsp position

    for n = 1:4
        velocity.( sprintf('v_%d', n ) ) = n*2;
        position.( sprintf('x_%d', n ) ) = n.^2;
    end

This is a good alternative when the names of the fields carry valuable information on the code, but maybe not this time.

[Azzi Abdelmalek]

You can also use table

velocity=s(:,1);
position=s(:,2);
out=table(velocity,position)

[cgo]

Thanks again.