How can I fill between two curves, but only when one curve is above the other?

Hello,

I'd like to fill the gap between two lines, but only when one line is above the other.

With the data file attached and the command:

plot(x,y1,'k',x,y2,'k:');
hold on;
xlim([x(1) x(end)]);
jbfill(x',y1',y2',[.8 .8 .8],'none',0,.5);
legend('y1','y2');
hold off;

I can plot:

which always fills the gap between y1 and y2. But I'd like it to be filled only when y1>y2.

Any help on this is very welcome.

Best,

Answer 1

[Alex Mcaulley]

You can do a little trick:

plot(x,y1,'k',x,y2,'k:');
hold on;
xlim([x(1) x(end)]);
y1tmp = y1;
y1tmp(y1<y2) = y2(y1<y2);
jbfill(x',y1tmp',y2',[.8 .8 .8],'none',0,.5);
legend('y1','y2');
hold off;

[Luciano Campos]

Thanks Alex, this works perfectly!

Best,

Answer 2

[KSSV]

load Data.mat ;
plot(x,y1,'k',x,y2,'k:');
hold on;
xlim([x(1) x(end)]);
% jbfill(x',y1',y2',[.8 .8 .8],'none',0,.5);
legend('y1','y2');
hold off;

idx = y1>y2 ; 
figure
X = [x(idx) ; flipud(x(idx))] ; 
Y = [y1(idx) ; flipud(y2(idx))] ; 
fill(X,Y,'r')

Answer 3

[Vinicius Pereira Mateus Borges]

Hi, I am new to MATLAB - I just started doing an online course a few weeks ago - so this is probably not a very good solution.

But it works!

plot(x,y1,'k',x,y2,'k:');
hold on;
xlim([x(1) x(end)]);
% initiate temporary variable
temp1 = zeros(1,numel(x)); 
temp2 = zeros(1,numel(x)); 

for i = 1:numel(x)
    if y1(i) > y2(i)
        temp1(i) = y1(i) % only store values of y1 if y1>y2
        temp2(i) = y2(i) % only store values of y2 if y1>y2
    end
end
jbfill(x',temp1,temp2,[.8 .8 .8],'none',0,.5); % only plot values when y1>y2
legend('y1','y2');
hold off;
shg