Given the variables how can i repeat a formula multiple times

Hello everybody, I am a newbie to matlab. Would really appreciate some help on this matter. I am looking to solve a formula like c_i = a_i.*b_i. I have to solve it a couple thousand times and for each step,I also need the answer as a variable. The variable a_i and b_i are avaiable like a_1,a_2,a_3,b_1,b_2 ... Regards, Fawad

Answer 1

[KSSV]

N = 100 ;
a = rand(N,1) ;   % random a 
b = rand(N,1) ;   % randon b 
c = zeros(N,1) ;  % initialize c which a*b 
% using loop
for i = 1:N
    c(i) = a(i)*b(i) ;
end
% vectorization
cv = a.*b ;

Answer 2

[Adam]

For a start, lose the variables a_1, a_2, etc. Use an array, a, of all of them. Likewise with b and the same with the result in c, then it is easy:

function c = calculateStuff( a, b )

c = a .* b;

end

This is vectorisation (or vectorization for Americans) and allows you to calculate the result on all your values far more quickly than if you called the function once in a for loop for every one of your variables.

Obviously this is so simple it doesn't need to be in a function as it is just a one-liner so feel free to just put the code where you need it instead.

Someone can probably post links to well-known places telling you why millions of named variables are bad, but I can never remember where to find it so until then just trust me - Use vectors, it is what Matlab is based around!