How to fill color between two curves?

clc
clear

x(1) = 0 ;
y(1) = 0 ;

for i = 1 : 1 : 99
    
    x(i+1) = i^2 ;
    y(i+1) = 50 * i ;
    
end

figure(1)
plot(x)
hold on
plot(y)
grid on

Answer 1

[Star Strider]

If you only want the region between the curves before or after they cross, use ‘logical indexing’.

Try this —

% clc
% clear

i = 1:99;
x = [0 i.^2];
y = [0 50*i];
iv = 1:numel(x);

Lv = x <= y;                                        % Logical Vector

figure(1)
plot(x, 'LineWidth',1, 'DisplayName','x')
hold on
plot(y, 'LineWidth',1, 'DisplayName','y')
patch([iv(Lv) flip(iv(Lv))], [x(Lv) flip(y(Lv))], 'r', 'EdgeColor','none', 'DisplayName','Before Inmtersection')
patch([iv(~Lv) flip(iv(~Lv))], [x(~Lv) flip(y(~Lv))], 'g', 'EdgeColor','none', 'DisplayName','After  Intersection')
hold off
grid on
legend('Location','best')

EDIT — (28 Sep 2023 at 11:25)

Æsthetic improvements.

.

[Aditya Zade]

Thank you.

[Star Strider]

As always, my pleasure!

[Aditya Zade]

Can you look into this as well?

https://www.mathworks.com/matlabcentral/answers/2026949-how-to-stack-up-multiple-cases-in-z-axis?s_tid=prof_contriblnk

Answer 2

[Mathieu NOE]

hello

see below

FYI, your code does not need a for loop. Take advantage of matlab native vectorized operations

% y1(1) = 0 ;
% y2(1) = 0 ;
% for i = 1 : 1 : 99
%    
%     y1(i+1) = i^2 ;
%     y2(i+1) = 50 * i ;
%     
% end

x = 0:99;
y1 = x.^2 ;
y2 = 50*x ;


figure(1)

X=[x,fliplr(x)];                %#create continuous x value array for plotting
Y=[y1,fliplr(y2)];              %#create y values for out and then back
fill(X,Y,[0.9 0.9 0.9]);                  %#plot filled area
hold on
plot(x,y1,'r',x,y2,'m','linewidth',2)

[Aditya Zade]

Thank you.