How can I fill between two curves, one color for when the test curve is above and a different color when it is below?

I'm hoping my aspirations for plotting aren't too ambitious for what MATLAB can handle. This is what I'm plotting right now. figure('Name','PTV'); hold on;plot(x,Base_Values.PTV{1},'--k','LineWidth',1.2);cellfun(@plot,Test_Case.PTV);

The cell Test_Case.PTV can have many elements or just one. How could I compare a plot from Test_Case.PTV to the first plot and have the area shaded red if it is above the first plot and green if below?

I would prefer to have a hatched fill, but I don't believe that's built into MATLAB, so I think I would need an outside function. But can this fill easily be done with two different colors for the corresponding areas between two curves?

And if so, I'm hoping it can be down for multiple elements at a time, although it will be quite messy, but I hope that the filled areas can be turned off with the plotted curve through plot browser. If that is not possible, I could create my function to only plot one at a time.

Answer 1

[KSSV]

x = linspace(0,2*pi) ;
y = sin(x) ;
% plot(x,y) ; hold on
%%negative sine
idx1 = y<0 ;
x1 = x(idx1) ;
y1 = y(idx1) ;
x1 = [x1 x1(1)] ;   % make a closed curve 
y1 = [y1 y1(1)] ;
patch(x1,y1,'r','edgecolor','none') ;
% Positive sine
idx2 = y>0 ;
x2 = x(idx2) ;
y2 = y(idx2) ;
x2 = [x2 x2(1)] ;   % make a closed curve 
y2 = [y2 y2(1)] ;
patch(x2,y2,'g','edgecolor','none') ;

You may set 'edgecolor' option to 'none'. so that there wont be any connecting line shown.

Answer 2

[KSSV]

x = linspace(0,2*pi) ;
y = sin(x) ;
plot(x,y) ; hold on
%%negative sine
idx1 = y<0 ;
x1 = x(idx1) ;
y1 = y(idx1) ;
x1 = [x1 x1(1)] ;   % make a closed curve 
y1 = [y1 y1(1)] ;
patch(x1,y1,'r') ;
% Positive sine
idx2 = y>0 ;
x2 = x(idx2) ;
y2 = y(idx2) ;
x2 = [x2 x2(1)] ;   % make a closed curve 
y2 = [y2 y2(1)] ;
patch(x2,y2,'g') ;

I hope the above example code might help you to get what you want...

[k5jyw153vcxb]

I think it's a good start, but it's creating the patch area from the x-axis. I cannot figure out how to get it to fill in between two curves

[Star Strider]

I don’t understand what you want, and I’m not going to ‘step on’ Dr. Kolokula’s Answer with my own.

This will colour the area between the two curves here. I’m not certain what you want to do, so while it should get you started, you will have to experiment with it.

x  = linspace(-1, 1);
y1 = exp(0.1*x);
y2 = 1 + exp(0.2*x);

figure(1)
plot(x, y1)
hold on
plot(x, y2)
patch([x fliplr(x)],[y1 fliplr(y2)], 'g')
hold off
grid

[k5jyw153vcxb]

Yes, that is a good start to what I want. But I want the area in between to be green when y1 is above y2 and the area to be red when y1 is below y2. I'm not too sure how to achieve this based on what you showed though, but perhaps experimenting with what Dr. Kolokula has shown too, I may be able to figure it out.

[k5jyw153vcxb]

This is what I've got so far:

figure(1)
plot(x, y1)
hold on
plot(x, y2)

%%negative sine
idx1 = y1 < y2 ;
xa = x(idx1) ;
y1a = y1(idx1);
y2a = y2(idx1);
patch([xa fliplr(xa)],[y1a fliplr(y2a)], 'r')
% Positive sine
idx2 = y1 > y2 ;
xb = x(idx2) ;
y1b = y1(idx2) ;
y2b = y2(idx2) ;
patch([xb fliplr(xb)],[y1b fliplr(y2b)], 'g')

hold off
grid

This works correctly for both regions now. I see there's a black line connecting two of my green regions that are not continuous. is there a way to get rid of this?

[Star Strider]

I need to have ‘x’, ‘y1’ and ‘y2’. Without them, I can’t reproduce your plot.

Answer 3

[Zaka Ullah]

How can we draw it...