loop and loglog problem

Hello, I wrote a code, but it didn't run. I think loops are wrong.I want to solve those functions and then to plot them in loglog graphs.What are my mistakes? Is there anyone who can help me?Please help.

 %Source Function

 fc=0.4;

 Ohm=20;

 x=0.01:0.01:50;

 for i=1,5000;

    for j=1,5000;

        for k=1,5000;

 x=f(i);

 x=f(j);

 x=f(k);

 S(i)=Ohm/(1+((f(i)\fc)^2));

 S(j)=(Ohm*((2*pi*fc)^2))/(1+((fc/f(j))^2)*(2*pi*f(j)));

 S(k)=(Ohm*((2*pi*fc)^2))/(1+((fc/f(k))^2));

        end
    end
end

 loglog(S(i));

 loglog(S(j));

 loglog(S(k));

 grid on;

Answer 1

[Image Analyst]

First of all, this is incorrect syntax:

for i=1,5000;

You need to do it like this:

 for i=1:5000   % No comma (colon instead of comma) , no semicolon.

Next, your S gets overwritten for i, j, and k. Was S supposed to be a 3D array S(i, j, k)???

[gulcin]

I want to calculate 3 separate functions for f(i),f(j) and f(k) which are from 0.01 to 50 Hz with interval 0.01 and then 3 loglog plots in 2D.

[gulcin]

f(i),f(j) and f(k) will be between 0.01 and 50 Hz with the interval 0.01

[Image Analyst]

Don't accept until you have it figured out. If you want 3 separate functions you have to give them separate names: f1, f2, f3, S1, S2, S3, or whatever. You can't use the same letter (f or S) for all three functions.

[gulcin]

OK. I changes the names, but it gives an error written below:

??? Attempted to access f(0.01); index must be a positive integer or logical.

Error in ==> Source_Function at 10 A=Ohm/(1+((f(i)/fc)^2));

HERE IS MY CODE:

 %Source Function
 fc=0.4;
 Ohm=20;
 i=0.01:0.01:50;
 j=0.01:0.01:50;
 k=0.01:0.01:50;
 for i=0.01,50;
     for j=0.01,50;
         for k=0.01,50;
 A=Ohm/(1+((f(i)/fc)^2));
 B=(Ohm*((2*pi*fc)^2))/(1+((fc/f(j))^2)*(2*pi*f(j)));
 C=(Ohm*((2*pi*fc)^2))/(1+((fc/f(k))^2));
         end
     end
 end
 loglog(f(i),A);
 loglog(f(j),B);
 loglog(f(k),C);
 grid on;

[Image Analyst]

Well, what IS f???? Why do you think your function will somehow automagically know what f is?

[gulcin]

f is the frequency and it is between 0.01 and 50 Hz with the interval 0.01.

[gulcin]

S(f) are the source functions of an earthquake station for displacement spectrum, velocity spectrum and acceleration spectrum.

[Image Analyst]

Where in your code do you define these?

[gulcin]

You said that I must give different names to S and now they are A,B,C. Here are the source functions:

 A=Ohm/(1+((f(i)/fc)^2));
 B=(Ohm*((2*pi*fc)^2))/(1+((fc/f(j))^2)*(2*pi*f(j)));
 C=(Ohm*((2*pi*fc)^2))/(1+((fc/f(k))^2));

[Image Analyst]

Yes, that's fine, but what is "f"? Where is "f" defined? You use it so it must be defined before you use it. A, B, anc C are fine because you're not using them, you're creating them, but they depend on "f" so "f" must have a value.

[gulcin]

Yes, that's right. f is the frequency and it is between 0.01 and 50 Hz. Its sampling frequency is 0.01. Actually,I have the problem with 'f'. It will be defined with a loop like this:

for i=0.01,50;
   for j=0.01,50;
       for k=0.01,50;
A=Ohm/(1+((f(i)/fc)^2));
B=(Ohm*((2*pi*fc)^2))/(1+((fc/f(j))^2)*(2*pi*f(j)));
C=(Ohm*((2*pi*fc)^2))/(1+((fc/f(k))^2));
        end
    end
end
-----------------------------------------------------------------------

OR It will be f=0.01:0.01:50 ?

I must create a serial.

[Image Analyst]

Perhaps it's f=0.01:0.01:50, but what do i, j, and k represent? And why don't A, B, and C have indexes anymore?

[gulcin]

i,j,k represents the numbers 0.01,0.02,....,50. Even if I put indexes to A,B,C it doesn't run.

[gulcin]

I am so stucked please help!