make the markers in the plot more visible-CodePudding

I want to draw the progress of the gradient descent.

I start with the function "f" and the partial derivation of the function and start the gradient descent with the parameters you see in the code.

When I plot the 3D graph of the function and the points of the gradient descent which i store during the iterations, the markers of the progress aren't good visible.

def f(X,Y):
    return (X**2)   (2*(Y**2))   (2*X*Y) - (6*X) - (16*Y)   (41)
     

def derivation_x(X, Y):
    return (2*X)   (2*Y) - (6)


def derivation_y(X,Y):
    return (2*X)   (4*Y) - (16)


def gradient_step(x, y,lr=0.0000001 ):
    new_x = derivation_x(x, y) * lr
    new_y = derivation_y(x, y) * lr
    return new_x, new_y


def lost_z(x,y):
    return f(x,y)


def gradientenDescent(startx, starty):
    
    new_x, new_y = gradient_step(startx, starty, lr=0.005 )

    diffx = startx - new_x
    diffy= starty - new_y
    return diffx, diffy

# I start the folling in a jupyter cell
_____________________________
start_x, start_y =  -20 ,-20  
points = []
for iteratrion in range(250):
    
        
    x_step, y_step = gradientenDescent(start_x, start_y)
    newlost = lost_z(x_step, y_step  )
    points.append([start_x, start_y, newlost])
    if iteratrion % 10 == 0:
        print("iteratrion:"   str(iteratrion))
        print("x:"   str(start_x)    "  y:"   str(start_y))
        print("Z:"   str(newlost))
        print("___________________")
    start_x, start_y =  x_step, y_step

___________________________________


size = 12
X, Y = np.linspace(-25,25,25), np.linspace(-25,25,25)
X, Y = np.meshgrid(X,Y)
fig = plt.figure(figsize= (size,size))
ax = fig.add_subplot(111, projection='3d')
ax.plot_surface( X ,Y,  f(X,Y), cmap="jet", alpha = 0.6)
ax.set_xlabel('x')
ax.set_ylabel('y')
ax.set_zlabel('z')



for i in range(len(points)): 
    ax.scatter(points[i,0],points[i,1],points[i,2],color='r', marker='x', alpha = 1) 
    


ax.elev = 270
ax.azim = 270  # xz view

ax.elev = 180
ax.azim = 180    # yz view

ax.elev = 15
ax.azim = 15 # xy view
plt.show()
_________________________

So now i want the markers be more visible as it is now.

here is the Image matplotlib draw so far

CodePudding user response：

The Scatters are hidden by the 3dSurface. To avoid this you can use the following:

ax = fig.add_subplot(111, projection='3d', computed_zorder=False)
...
ax.plot_surface(X, Y, f(X, Y), cmap="jet", alpha=0.6,zorder=1)
...
for i in range(len(points)):
    ax.scatter(points[i,0],points[i,1],points[i,2],color='r', marker='x', alpha = 1, zorder=2, s=21)

use s=21 to change the size of xmarks. maybe it would also look nice if a cmap would be used for the scatters instead of an static color