How to plot gradients ?
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Star Strider
2020-10-1
2 个投票
14 个评论
Star Strider
2020-10-1
This should get you started:
x = linspace(3, 4, 25);
y = linspace(5, 6, 25);
[X,Y] = meshgrid(x,y);
z = @(x,y) x.^2+y.^5+3*x+4*y;
Z = z(X,Y);
It is not a very interesting plot.
qweasd
2020-10-1
Star Strider
2020-10-1
My pleasure!
qweasd
2020-10-2
Star Strider
2020-10-2
You aren’t really bad. You simply need to experiment with it.
The rest of the code is essentially what’s in the documentation example that I linked to, from the gradient call to the end of the example. You only need to make a few small changes to it.
Star Strider
2020-10-5
Like that!
The code I wrote for your problem:
x = linspace(3, 4, 25);
y = linspace(5, 6, 25);
[X,Y] = meshgrid(x,y);
z = @(x,y) x.^2+y.^5+3*x+4*y;
Z = z(X,Y);
[px,py] = gradient(Z);
figure
contour(X,Y,Z)
hold on
quiver(X,Y,px,py)
hold off
They appear to match.
qweasd
2020-10-5
Star Strider
2020-10-5
As always, my pleasure!
saurav Tiwari
2021-9-29
x = linspace(3, 4, 25);
y = linspace(5, 6, 25);
[X,Y] = meshgrid(x,y);
z = @(x,y) x.^2+y.^5+3*x+4*y;
Z = z(X,Y);
[px,py] = gradient(Z);
figure
contour(X,Y,Z)
hold on
quiver(X,Y,px,py)
hold off
saurav Tiwari
2021-9-29
it's not working
Yes, it is!
x = linspace(3, 4, 25);
y = linspace(5, 6, 25);
[X,Y] = meshgrid(x,y);
z = @(x,y) x.^2+y.^5+3*x+4*y;
Z = z(X,Y);
[px,py] = gradient(Z);
figure
contour(X,Y,Z)
hold on
quiver(X,Y,px,py)
hold off
.
Niklas Kurz
2022-3-13
编辑：Niklas Kurz
2022-3-13
I would opt to normalise the Arrows for better scaling:
Norm = sqrt(px.^2+py.^2)
quiver(X,Y,px./Norm,py./Norm,0.5)
Otherwise the code is pretty neat!
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