I want draw a graph correctly

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pty0220
pty0220 on 18 Jan 2016
Edited: Mike Garrity on 19 Jan 2016
I write code like this
function z = F3(x,y)
z = 4- x.^2- 2*y.^2;
figure(1)
[X,Y] = meshgrid(0:0.1:2);
mesh(X,Y,F3(X,Y))
axis([0 2 0 2 0 6])
and than
graph is came out like this
I don't want to see value of Z under '0'
How can I do that??
Thought I give the value of the Z axis range from 0 to 6, but it is steel came out like this ,,,
  3 Comments
pty0220
pty0220 on 19 Jan 2016
R2014a for mac thanks ~
Walter Roberson
Walter Roberson on 19 Jan 2016
I confirm that with that release on Mac I see the same results. The clipping property of the axes is seemingly being ignored.

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Answers (1)

Thorsten
Thorsten on 18 Jan 2016
With your axis command you cut off the z values at 0 (with the third 0 in axis([0 2 0 2 0 6]). Instead, use:
Z = F3(X,Y);
mesh(X,Y,Z);
axis([0 2 0 2 min(Z(:)) max(Z(:))])
  3 Comments
Thorsten
Thorsten on 19 Jan 2016
I see. You could set the negative Z values to 0 or NaN:
Z(Z<0) = 0;
or
Z(Z<0) = NaN;
In the first case you have the a mesh at the positions were Z < 0, with NaN the cut-off is ragged. So both solutions may be better than the original plot, but they are not perfect.
Mike Garrity
Mike Garrity on 19 Jan 2016
Edited: Mike Garrity on 19 Jan 2016
You're seeing something called
ClippingStyle = 'rectangle'
In that type of clipping, the geometry is clipped at the 2D rectangle that surrounds the axes. That was the only type of clipping that MATLAB Graphics supported until R2014b. Since that release, you have another choice:
ClippingStyle = '3dbox'
And I think that will actually be the default in this case. So if you upgrade to a newer version, you should get what you want.
In newer versions, if you don't like the clipping style that was chosen for you, you can change it like so:
set(gca,'ClippingStyle','3dbox')
or
set(gca,'ClippingStyle','rectangle')

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