How to color an area at plot surface...

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Masoud Ghanbari on 17 Apr 2013
How can i color the area between 2 functions like
f(x)=x^2
g(x)=-x^2+1

Thomas on 18 Apr 2013
I found a better way... try
x=1:10;
f=x.^2;
g=x.^2+1;
patch([x x(end:-1:1)], [f g(end:-1:1)],'y')
This sets up x=1...10, g=x² and f=x²+1 and then plots the area between the curves as a yellow polygon/patch. Compare the matlab help for patch.
Here i simply draw all points forf first in positive x direction and then jump to the last point of g and draw the points of g backwards from x=10...1. All in all a complete polygon. Btw, 'y' is the color yellow.

Masoud Ghanbari on 18 Apr 2013
Hi
It worked but i cant understand the code
for example what if we want to color the area like f-g<2 ???
Thomas on 18 Apr 2013
i dont understand what you mean by f-g<2. You have to e.g. put the vector with the upper border curve values in f and the lower border data into g (or the other way round, it doesnt matter) and then call the patch command.
Masoud Ghanbari on 19 Apr 2013
Thanks... Hope to support me at my further problems

Thomas on 17 Apr 2013
You could use sth like
area(g);
hold on;
area(f);
and then select f's fill color to be the backgroud color.
Of coures this only works as long as f<g for all x.
If this is not the case you could first do
upperCurve = max(f,g)
lowerCurve = min(f,g)
and then plot upperCurve and lowerCurve as stated above. If they are sufficiently high-res compared to your plot resolution it might be sufficient, however it wouldn't be "clean". Maybe there is another solution anyone can bring up...

Masoud Ghanbari on 18 Apr 2013
hi
It does not works
would you please bring me the full code

Muruganandham Subramanian on 18 Apr 2013
hi,
for e,g.
x=[1 2 3 4 5];
for i=1:numel(x)
f(i)=x(i)^2;
g(i)=-x(i)^2+1;
end
plot(x,f,x,g)
hold on;
area(f-g)
hold on;
area(g-f)
Do you expecting like this?