erorr in for loop

could you please help me to correct these small calculations

 w=0:0.02:5;
 for i=1:length(w)
 a(i)=w.^4-12.*(w.^2);
 b(i)=w.^8-144.*(w.^4);
 c(i)=9.*(w.^6)+256.*(w.^2);
 Real(i)= a(i)/(b(i)+c(i));
 end

thank you

Answer 1

[CS Researcher]

.^ is for element wise operation. Use this:

 w=0:0.02:5;
 for i=1:length(w)
     a(i)=w(i)^4-12*(w(i)^2);
     b(i)=w(i)^8-144*(w(i)^4);
     c(i)=9*(w(i)^6)+256*(w(i)^2);
     Real(i)= a(i)/(b(i)+c(i));
 end

Or better:

w=0:0.02:5;
a = w.^4-12.*(w.^2);
b = w.^8-144.*(w.^4);
c = 9.*(w.^6)+256.*(w.^2);
Real= a./(b+c);

[Lilya]

Thank you for reply Could you please tell me how can I find the w value if the x=1?

[CS Researcher]

What is x?

[Lilya]

Sorry for the mistake Finding the w value that makes the equation =1 (i.e Real)

Answer 2

[Image Analyst]

Try this:

w=0:0.02:5;
a = w.^4-12.*(w.^2);
b = w.^8-144.*(w.^4);
c = 9.*(w.^6)+256.*(w.^2);
ratios = a ./ (b+c);
plot(w, ratios, 'b*-');
grid on;

% 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');

% Find w where ratios == 1
differences = ratios-1;
[minDifference, indexOfMin] = min(differences)
% Plot a circle there
hold on;
plot(w(indexOfMin), ratios(indexOfMin), 'ro', 'MarkerSize', 15, 'LineWidth', 2);
message = sprintf('ratios is closest to 1 at index %d where ratios(%d) = %f',...
  indexOfMin, indexOfMin, w(indexOfMin));
uiwait(helpdlg(message));

[Lilya]

thanks alot