CODEWITHSUNDEEP
matlabplot
KatyB
KatyB

Reputation: 3990

fill underneath a curve with a gradient fill

I can fill an area underneath a specific part of a curve as follows:

x = 0:0.01:2*pi;           
y1 = sin(x)+10; 
y2 = repmat(5,length(y1),1);
plot(x,y1);
hold on;

% fill area between 1 and 2
val = [1,2];
for i = 1:2;
    tmp = abs(x-val(i));
    [~,idx(i)] = min(tmp);
end
id = idx(1):1:idx(2);

x2 = x(id);
y1a = y1(id);
y2a = y2(id);
y2a = y2a';

X=[x2,fliplr(x2)];
Y=[y1a,fliplr(y2a)];

fill(X,Y,'b');

enter image description here

Is it possible, however, to use a gradient fill instead of a solid color?

It would be great, for example, to use a jet colormap instead. Is this possible?

Upvotes: 3

Views: 2402

Answers (1)

RTL
RTL

Reputation: 3587

Method One

Here we will need the the handle of the patch created by fill the simplest way would be to change the last line to

Hpatch = fill(X,Y,'b');

Then we can set the colour data to be based on the y values and set the face colour to be interpolated

cdata=get(Hpatch,'ydata');
cdata=(cdata-min(cdata))/(max(cdata)-min(cdata)); %// normalise
set(Hpatch,'CData',cdata,'FaceColor','interp')

The three lines above get the ydata of the patch, normalise it, then set it to be the colour data of the patch and set the shading to interpolated.
The jet color map is default but to ensure jet is used add the line colormap('jet') after the code above.

note: normalising is optional as it will be automatically normalised however I personally would prefer to control it myself especially if handling multiple objects.

Output

enter image description here

Method Two

More simply, but less instructive, let Matlab do it for you, you can set the colour to be based on Y in the call to fill: fill(X,Y,Y)

Upvotes: 4

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