What is the error of my plot?

if true
  % code
endm5=1.78
c6=0.00036
c7=0.02
c8=0.00004
c9=0.1
k6=167.00
k8=623.00
F = 80
for w= 20:100:1000
  x5(end+1) = F/(sqrt(((k6+k8)-(m5*w))^2+((c6+c7+c8+c9)*w)^2)) 
end
plot (w,x5)

I can't see why the plot is wrong. Could please somebody help?

Answer 1

[Image Analyst]

You're plotting x5 vs the LAST value of w (a scalar that you used as the loop index), not the whole array. Try reassigning w to the whole array before plotting:

w = 20 : 100 : 1000;
plot(w, x5)

[Gabriel Oliviero]

Yes, you're right, that was problem I fixed it, but now I have this error

??? Error using ==> plot Vectors must be the same lengths.

Do you know why?

[Gabriel Oliviero]

I fixed that declaring x5 = [].

Thank you for your help!!!

[Image Analyst]

You might like this code better:

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;

m5=1.78
c6=0.00036
c7=0.02
c8=0.00004
c9=0.1
k6=167.00
k8=623.00
F = 80
w = 0 : 10 : 1000;
x5 = zeros(size(w));
for index = 1 : length(w)
  x5(index) = F/(sqrt(((k6+k8)-(m5*w(index)))^2 + ((c6+c7+c8+c9)*w(index))^2))
end
plot (w,x5, 'b*-', 'LineWidth', 2, 'MarkerSize', 12)
grid on;
xlabel('w', 'FontSize', fontSize);
ylabel('x5', 'FontSize', fontSize);
title('x5 vs. w', 'FontSize', fontSize);
ylim([0, 1.5]);

% Set up figure properties:
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
% Get rid of tool bar and pulldown menus that are along top of figure.
set(gcf, 'Toolbar', 'none', 'Menu', 'none');
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by Gabriel', 'NumberTitle', 'Off')