Conditional Data Selection/Separation

Hi, I have this question, kindly answer it:

PROBLEM STATEMENT:

1- My function has three variables-F,k and X.

2- I need to evaluate the function, f(F,k,X), 10,000 times to get outputs.

3- The variables F, k and X are random. They combine in many different ways to give the outputs.

4- I am only interested in those values that combine to satisfy this condition : f(F,k,X)<1.267.

5- I need to Matlab to separate these values and the corresponding output, f(F,k,X)<1.267.

I have simulation data for F, k, and X, I have computed the outputs, f(F,k,X), and f(F,k,X)<1.267 as well (each 10,000 times). I saved these 5 columns of data in a file named : 'Simd'

I went like this:

Simd;
F=Simd(:,1);
k=Simd(:,2);
X=Simd(:,3);
f(F,k,X)=F.*k.*X

 if (f(F,k,X)<1.267)
 M=[F  k   X  f(F,k,X)<1.267];
 end

My question is in the last three statements, please how do i get a the vector M containing values of F k and X satisfying f(F,k,X)<1.267 in a single file, that is in tabular form? Please what is the problem with my approach? Cheers.

Answer 1

[Oleg Komarov]

I suggest to read the Language Fundamentals and specifically Matrices and Arrays > Indexing > Matrix Indexing

idx = Simd(:,4) <1.267;
Simd(idx,1:4)

Thus, you don't need loops of if statements.