Loop over an array

Dear MatLab comunity,

I have a problem with a for loop.

I have two arrays of angles Theta1 and Theta2 (attached).

I have defined the following:

rTheta1 = load('theta1.dat');
rTheta2 = load('theta2.dat');

Theta1 = Theta1(:,2); %% which are the Theta1 angles
Theta2 = Theta2(:,2); %%       //      Theta2 angles

Theta1_cis = Theta1((Theta1 > -90) & (Theta1 < 90)); % Array of values when theta1 is in Cis 
Theta1_trans = Theta1(Theta1 > 90 | Theta1 < -90); % Array of values when theta1 is in Trans

What I need now is to define an array such that when Theta1 is whitin the cis range then I collect the value in the variable Theta2_T1cis otherwise it goes in Theta2_T1trans, or when Theta1 is in the trans range then it goes in Theta2_T1trans.

I tried to put up a loop but I am very nabish so please help me on this:

i = 1;
for i = 1:[Theta1]
    if Theta1((Theta1 > -90) & (Theta1 < 90))
         Theta2_T1cis(i) = Theta2(i)
    else Theta2_trans(i) = Theta2(i)
    i= i+1;        
    end
end   

this is not working of course. How can I solve it?

Hope the question is clear, otherwise I will reformulate.

Thanks in advance,

Alessandro

Answer 1

[Jan]

There is no need for a loop:

T1_cis_index   = (Theta1 > -90) & (Theta1 < 90);
T1_trans_index = (Theta1 > 90) | (Theta1 < -90);
Theta1_cis     = Theta1(T1_cis_index); 
Theta1_trans   = Theta1(T1_trans_index);
Theta2_T1cis   = Theta2(T1_cis_index); 
Theta2_T1trans = Theta2(T1_trans_index);

By the way, this is no the way loops are working. A cleaner version:

% i = 1;  Nope
for i = 1:numel(Theta1)  % Not: [Theta1]
    if (Theta1(i) > -90) & (Theta1(i) < 90))  % Use Theta1(i), not the complete vector
        Theta2_T1cis(i) = Theta2(i)
    else
        Theta2_trans(i) = Theta2(i)
        % Nope: i= i+1;        
    end
end

[Alessandro Ruda]

Thanks for the answer,

I tried them but they don't work. The loops gives me two arrays:

• Theta2_T1cis ordered in columns and not rows with zeroes and Theta2 values depending on when the if conditions is satisfied, but I don't want the zeroes.
• Theta2_T1trans that is the basically the same exact array as Theta2.

The first method doesn't seem to work either in my hands.

[Alessandro Ruda]

Ok, it actually works. But I had to change it this way to obtain what I wanted specifically.

for i = 1:numel(Theta1)
    if ((Theta1(i) > -90) & (Theta1(i) < 90))
        Theta2_T1cis_raw(i) = Theta2(i);      
    else
        Theta2_T1trans_raw(i) = Theta2(i);
    end
end

tTheta2_T1cis = Theta2_T1cis_raw(Theta2_T1cis_raw~=0);
Theta2_T1cis = transpose(tTheta2_T1cis);

tTheta2_T1trans = Theta2_T1trans_raw(Theta2_T1trans_raw~=0);
Theta2_T1trans = transpose(tTheta2_T1trans);

I don't know if it can be made cleaner!

Thank you anyway!

[Jan]

The loop is not needed. A shorter, leaner and faster solution:

match           = (Theta1 > -90) & (Theta1 < 90);
Theta2_T1cis    = Theta2(match);
tTheta2_T1trans = Theta2(~match);