# Why isn't my y value changing?

1 view (last 30 days)
Xavier Bardwell on 23 Nov 2021
Answered: Image Analyst on 23 Nov 2021
I have a while loop where i iterate through polyval calculations an unkown amount of times based on the r^2 value. My loop currently runs infinitely because my y values are not changing as the order changes. WHy isnt my y value changing and how can i fix it?
while rSQ < .95
y = polyval(polyfit(x,y,currOrder), x)
rSQTop = (yOG - y).^2
rSQBot = (yOG - yAVG).^2
rSQ = 1 - (sum(rSQTop) / sum(rSQBot))
if rSQ > .95
plot(x,y,'b-')
else
plot(x,y,'r--');
currOrder = currOrder + 1;
end
end
Xavier Bardwell on 23 Nov 2021
x = [-2.0000 -0.1130 -0.0545 0.0168 0.5409 0.5414 1.6444]
y = [50.1774 0.0007 0.0001 -0.0000 -0.0316 -0.0315 26.1672]

Image Analyst on 23 Nov 2021
I think you are trying to do this:
% Demo by Image Analyst
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 = 22;
x = linspace(0, 2*pi, 400);
y = cos(x) + 0.3 * rand(1, length(x));
p1 = plot(x,y,'b-');
hold on;
rSQ = 0;
loopCounter = 1;
maxIterations = 100;
currentOrder = 1;
requiredRSquared = 0.95;
while rSQ < requiredRSquared && loopCounter < maxIterations
fprintf('On iteration %d\n', loopCounter);
coefficients = polyfit(x,y,currentOrder);
yFitted = polyval(coefficients, x);
yAVG = mean(yFitted);
rSQTop = (yFitted - y).^2;
rSQBot = (yFitted - yAVG).^2;
rSQ = 1 - (sum(rSQTop) / sum(rSQBot));
message = sprintf('On iteration %d rSQ = %f. Order = %d', loopCounter, rSQ, currentOrder);
fprintf('%s\n', message)
if rSQ > requiredRSquared
p2 = plot(x, yFitted, 'g-', 'LineWidth', 5);
else
p2 = plot(x, yFitted, 'r-', 'LineWidth', 5);
currentOrder = currentOrder + 1;
end
grid on;
title(message, 'FontSize', 18);
g = gcf;
g.WindowState = 'maximized';
promptMessage = sprintf('Showing iteration %d.\nDo you want to Continue processing,\nor Quit processing?', loopCounter);
titleBarCaption = 'Continue?';
buttonText = questdlg(promptMessage, titleBarCaption, 'Continue', 'Quit', 'Continue');
if contains(buttonText, 'Quit', 'IgnoreCase', true)
break; % or break or continue.
end
loopCounter = loopCounter + 1;
% Get rid of last plot.
if rSQ < requiredRSquared
delete(p2);
end
end

R2021a

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