Changing color of plot lines in a loop - matlab

Question

I have a question about changing the color of lines in a plot in MATLAB. I have written a code where I want to change the color of lines in a plot that is embedded in several for loops (the code is shown below). In the code, a new plot is created (with its own figure) when the "if loop" condition is satisfied. I want each plot to have lines with different colors (from other plots), so I created a variable = "NewColor" to increment and change the line colors. However, the following problem has been occurring:
Suppose I am in debug mode and I have stopped at the plot command. I run the next step and a plot is created with a blue line. I check the value of NewColor and find NewColor = 0.1. Next, I use the "run to cursor" command to step to the next time the plot command is activated. When I do this I am still within the "i for loop", so NewColor has not changed. I check the editor to find that NewColor = 0.1. Therefore, when I run the next step a blue line should show up on the current plot. To the contrary and my disbelief an orange line shows up (in addition to the blue line). I don't understand since in both steps of the debugger NewColor = 0.1, and the code is written so the color of the lines = [0,NewColor,0]. If anyone can find the error of my ways it would be greatly appreciated. Thanks
ThetaPlot = [40,50]; % Put incident angle as input
Count1 = 0;
Count2 = 0;
NewColor = 0;
for m = 1:length(ThetaPlot)
NewColor = 0.1;
Title = sprintf('Angle(%d)',ThetaPlot(m));
figure('name',Title)
Count1 = 0;
for i = 1:length(xrange)-1 % X Coordinate of Start Node
for j = 1:length(yrange)-1 % Y Coordinate of Start Node
Count1 = Count1+1;
for k = 2:length(xrange) % X Coordinate of End Node
for l = 2:length(yrange) % Y Coordinate of End Node
Count2 = Count2+1;
if ReflRayData(Count2,ThetaPlot(m) - ThetaIncident(1) + 1,Count1) == 1
x = [xrange(i),xrange(k)];
y = [yrange(j),yrange(l)];
plot(x,y,['-',[0,NewColor,0],'o']);
hold on;
end
end
Count2 = 0;
end
end
end
NewColor = NewColor + 0.02;
end
Full Code:
%% Calculating Angles of Reflection
run = 1; % Set run = 1 for calculations
if run == 1
xrange = [0:1:14.5]'; % Coordinates to try for Panel Geometry (in)
yrange = [0:1:36]'; % Coordinates to try for Panel Geometry (in)
ThetaIncident = [-90:1:90]'; % Incident Angle of Ray (measured relative to normal direction with clockwise postive)
OvenGlassXrange = [14.5:0.1:36.5]; %Range of X coordinates for Oven Glass
ReflRayData = zeros((length(xrange)-1)*(length(yrange)-1),length(ThetaIncident),(length(xrange)-1)*(length(yrange)-1)); % Matrix containing Reflected Ray Data
Count1 = 0;
Count2 = 0;
for i = 1:length(xrange)-1 % X Coordinate of Start Node
for j = 1:length(yrange)-1 % Y Coordinate of Start Node
Count1 = Count1+1;
for k = 2:length(xrange) % X Coordinate of End Node
for l = 2:length(yrange) % Y Coordinate of End Node
Count2 = Count2+1;
for m = 1:length(ThetaIncident)
xStart = xrange(i);
yStart = yrange(j);
xEnd = xrange(k);
yEnd = yrange(l);
m1 = (yEnd - yStart)/(xEnd - xStart); % Slope between Start and End Nodes
b1 = yStart - m1*xStart;
m2 = 1/m1; % Slope of normal direction
b2 = (yEnd - 0.5*(yEnd - yStart)) - m2*(xEnd - 0.5*(xEnd - xStart));
ArbXCoor = 1; % Arbitary Point X Coordinate on Normal Line
ArbYCoor = m2*ArbXCoor+b2; % Arbitary Point Y Coordinate on Normal Line
ThetaReflected = -ThetaIncident(m); % Reflected Angle
ArbXCoorRot = ArbXCoor*cosd(ThetaReflected) - ArbYCoor*sind(ThetaReflected); % Arbitary Point X Coordinate on Reflected Line
ArbYCoorRot = ArbYCoor*cosd(ThetaReflected) + ArbXCoor*sind(ThetaReflected); % Arbitary Point Y Coordinate on Reflected Line
m3 = (ArbYCoorRot - (yEnd - 0.5*(yEnd - yStart)))/(ArbXCoorRot - (xEnd - 0.5*(xEnd - xStart))); % Slope of Reflected Line
b3 = (yEnd - 0.5*(yEnd - yStart)) - m3*(xEnd - 0.5*(xEnd - xStart));
ElemLength = sqrt((yEnd - yStart)^2 + (xEnd - xStart)^2);
if min(OvenGlassXrange) < -b3/m3 && -b3/m3 < max(OvenGlassXrange) && -1 < m1 && m1 < 0 && m1 ~= -Inf && m1 ~= Inf && ElemLength < 3
ReflRayData(Count2,m,Count1) = 1;
end
end
end
end
Count2 = 0;
end
end
%% Plotting
ThetaPlot = [40,50]; % Put incident angle as input
Count1 = 0;
Count2 = 0;
NewColor = 0;
for m = 1:length(ThetaPlot)
NewColor = 0.1;
Title = sprintf('Angle(%d)',ThetaPlot(m));
figure('name',Title)
Count1 = 0;
for i = 1:length(xrange)-1 % X Coordinate of Start Node
for j = 1:length(yrange)-1 % Y Coordinate of Start Node
Count1 = Count1+1;
for k = 2:length(xrange) % X Coordinate of End Node
hold on;
for l = 2:length(yrange) % Y Coordinate of End Node
Count2 = Count2+1;
if ReflRayData(Count2,ThetaPlot(m) - ThetaIncident(1) + 1,Count1) == 1
x = [xrange(i),xrange(k)];
y = [yrange(j),yrange(l)];
plot(x,y,['-',[0,NewColor,0],'o']);
hold on;
end
end
Count2 = 0;
end
end
end
NewColor = NewColor + 0.02;
end

Answer 1

instead of plot(x,y,['-',[0,NewColor,0],'o']); try:
plot(x,y,'linestyle','-','marker','o','color',[0,NewColor,0])

Answer 2

According to the Matlab documentation, by calling hold on Matlab uses the next color.
hold on retains plots in the current axes so that new plots added to the axes do not delete existing plots. New plots use the next colors and line styles based on the ColorOrder and LineStyleOrder properties of the axes.
Therefore, in your code when you call hold on inside the for, it just uses the next color.
My solution is to put figure; hold on; before for loop and remove that one in you loop