how to vectorize this "For Loop" ?

close all
clear all
clc
tic;
for k=1:0.5:10;
    for a=1:0.5:5;
        num=k;
        den=[1 a 0];
        sys=tf(num,den); 
        bode(sys);grid on;hold on;

      end
  end
  time=toc

Answer 1

[Walter Roberson]

k=1:0.5:10;
a=1:0.5:5;
[K, A] = ndgrid(k, a);
Numerator = num2cell(K(:));
nusz = size(Numerator);
Denominator = num2cell( [ones(nusz), A(:), zeros(nusz)], 2);

tfs = tf(Numerator, Denominator);

Now at this point you have two choices:

1)

bode(tfs); grid on

This is not the same as your original code: it produces an array of plots. To be honest, it is not understandable even in full screen mode -- it just looks like a series of straight lines across the screen. However, the execution time is not so bad considering.

2)

for K = 1 : 171; bode(tfs(K)); hold on; end; grid on

This is the same as your original code. It would create a single pair of plots with 171 lines each (but most of which overlay each other.) This takes quite a while to execute.

The drawing of the plots takes much much longer than the creation of the transfer functions -- to the point where it is hardly even worth bothering to vectorize the creation of the transfer functions considering the loss in clarity about what is being plotted.

Answer 2

[scadaprog]

Hi, This is one way of doing it:

 k=1:.5:10; a=1:.5:5;

 num=repmat(k',numel(a),1);

 a = [ones(numel(a),1) a' zeros(numel(a),1)];
 den = repmat(a, numel(k),1);

 sys = tf(num2cell(num),num2cell(den,2));

 bode(sys);