Given the variables how can i repeat a formula multiple times

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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

Answers (2)

KSSV on 18 Jul 2016
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) ;
% vectorization
cv = a.*b ;

Adam on 18 Jul 2016
Edited: Adam on 18 Jul 2016
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;
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!


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