Computing powers in matlab

find A whose ith element is A = ( 2.^i ) X ./ Y .... where X and Y are vectors of equal length

without looping. ie. X = [1 2 3] Y = [4 5 6].

I know how to do X ./ Y but the ith element of (2.^i) is confusing me and I do not know how to do it without looping. Thanks

Edit. Thank you 2.^(1:length(x)) worked. What if it was -2 instead of 2??? I tried fooling around with it but I had no luck

Answer 1

[Andreas Goser]

doc power

Answer 2

[Mischa Kim]

Does this do it?

 X = [1 2 3]; Y = [4 5 6];
 A = (2.^sort(randperm(length(X)))).*X./Y
 A =
    0.5000    1.6000    4.0000

[Walter Roberson]

A little obfuscation to start the day right ;-)

Answer 3

[Walter Roberson]

2.^(1:3)

[Mischa Kim]

Am I reading the equation for A incorrectly? Does it not depend on X and Y? And yes, I did it for the general case of arbitrary vector sizes :)

[Walter Roberson]

the ith element of (2.^i) is confusing me

so I showed an example of creating that portion. I could have generalized that portion as

2.^(1:length(X))

which is what your code does in an obscure way.

[Mischa Kim]

Ok, I understand. For the vector size portion, I have to admit, I tried to come up with a challenge for myself.

[Walter Roberson]

What if it was -2, mark asked.

(-2).^(1:length(X))