# erorr in for loop

1 view (last 30 days)
Lilya on 2 May 2016
Commented: Lilya on 3 May 2016
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

CS Researcher on 2 May 2016
.^ 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 on 2 May 2016
Edited: Lilya on 2 May 2016
Sorry for the mistake Finding the w value that makes the equation =1 (i.e Real)

Image Analyst on 2 May 2016
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.
% 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 on 3 May 2016
thanks alot