[Matplotlib-users] Add and remove points to a scatter plot repeatedly

Community matplotlib-users
1

I am trying to add and remove points to a scatter plot repeatedly, each time
with a different set of points, while a wireframe plot is in the
background.
is there a way to do so with out closing the all figure window and the
background wireframe plot?

Thanks

Here is my python code:
import gdal
from mpl_toolkits.mplot3d.axes3d import *
import matplotlib.pyplot as plt
from pathlib import Path

#import the raster tif file and convert to 2d array
dataset = gdal.Open("dem_demo.tif")
dem_arr = dataset.ReadAsArray()

#slicing
#dem_arr[start row:end row,start col:end col]
sliced_dem_arr = dem_arr[100:151,100:151]
rowCount = sliced_dem_arr.shape[0]
colCount = sliced_dem_arr.shape[1]

#set the X, Y, Z arrays for plotting process
rowArr = np.arange(1,rowCount+1)
colArr = np.arange(1,colCount+1)
X, Y = np.meshgrid(rowArr, colArr)
Z = sliced_dem_arr

#set 3d view ans labels
ax = plt.axes(projection='3d')
ax.set_xlabel('x')
ax.set_ylabel('y')
ax.set_zlabel('z')

############plotting the dtm ########################
###wireframe
ax.plot_wireframe(X, Y, Z, color='green')

#Add points #01
points_list = [(2,6),(30,14),(39,15)]
for p in points_list:
    ax.scatter(p[0], p[1], sliced_dem_arr[p[0],p[1]], c = 'r')
plt.show()

#Add points #02
points_list2 = [(5,23),(24,4),(12,45)]
for p in points_list2:
    ax.scatter(p[0], p[1], sliced_dem_arr[p[0],p[1]], c = 'r')
plt.show()

<http://matplotlib.1069221.n5.nabble.com/file/t5275/example.jpeg>

···

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2

You could use animation. See python - How to create 3D scatter animations - Stack Overflow

Here is a short example based on the Matplotlib wireframe example (3D wireframe plot — Matplotlib 3.1.2 documentation) and your two sets of points. This will work in a Jupyter notebook if you use the %matplotlib notebook magic command but the animation does not work with jupyter lab.

import numpy as np
from mpl_toolkits.mplot3d import axes3d
import matplotlib.pyplot as plt
import matplotlib.animation

def update_graph(num):
    # alternate between the 2 sets of points
    num = 3 * (num % 2)
    data = points[num:num+3]
    dots.set_data (data[:,0], data[:,1])
    dots.set_3d_properties(data[:,2])
    return dots,

fig = plt.figure(figsize=(8,8))
ax = fig.add_subplot(111, projection='3d')

# Plot a basic wireframe.
X, Y, Z = axes3d.get_test_data(0.05)
ax.plot_wireframe(X, Y, Z, rstride=10, cstride=10, color='green')

# set up the points to be plotted
points_list = np.array([(2,6),(30,14),(39,15)])
points = np.append(points_list,
                  Z[points_list[:,0], points_list[:,1]].reshape(3,1),
                  1)
points_list2 = np.array([(5,23),(24,4),(12,45)])
points = np.append(points,
                  np.append(points_list2, Z[points_list2[:,0], points_list2[:,1]].reshape(3,1), 1),
                  0)

dots, = ax.plot(points[:,0][:3], points[:,1][:3], points[:,2][:3],
                linestyle="", marker="o", c='r')

ani = matplotlib.animation.FuncAnimation(fig, update_graph, 2,
                               interval=500, blit=True)
plt.show()

I ran the example with matplotlib 3.1.1 in python 3.8.

Hth,
Scott

···

On Dec 3, 2019, at 10:09 AM, regev81 <regev81@gmail.com> wrote:

I am trying to add and remove points to a scatter plot repeatedly, each time
with a different set of points, while a wireframe plot is in the
background.
is there a way to do so with out closing the all figure window and the
background wireframe plot?

Thanks

Here is my python code:
import gdal
from mpl_toolkits.mplot3d.axes3d import *
import matplotlib.pyplot as plt
from pathlib import Path

#import the raster tif file and convert to 2d array
dataset = gdal.Open("dem_demo.tif")
dem_arr = dataset.ReadAsArray()

#slicing
#dem_arr[start row:end row,start col:end col]
sliced_dem_arr = dem_arr[100:151,100:151]
rowCount = sliced_dem_arr.shape[0]
colCount = sliced_dem_arr.shape[1]

#set the X, Y, Z arrays for plotting process
rowArr = np.arange(1,rowCount+1)
colArr = np.arange(1,colCount+1)
X, Y = np.meshgrid(rowArr, colArr)
Z = sliced_dem_arr

#set 3d view ans labels
ax = plt.axes(projection='3d')
ax.set_xlabel('x')
ax.set_ylabel('y')
ax.set_zlabel('z')

############plotting the dtm ########################
###wireframe
ax.plot_wireframe(X, Y, Z, color='green')

#Add points #01
points_list = [(2,6),(30,14),(39,15)]
for p in points_list:
   ax.scatter(p[0], p[1], sliced_dem_arr[p[0],p[1]], c = 'r')
plt.show()

#Add points #02
points_list2 = [(5,23),(24,4),(12,45)]
for p in points_list2:
   ax.scatter(p[0], p[1], sliced_dem_arr[p[0],p[1]], c = 'r')
plt.show()

<http://matplotlib.1069221.n5.nabble.com/file/t5275/example.jpeg&gt;

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3

Thanks, Scott.

But i create the scatter plots in runtime and i want to present them when i
want by a function and not by a time interval.
Is there a way to do so ?

···

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4

You can remove the scatter object, call scatter again and then call draw. Or if they are similar enough just change the x and y data of the existing scatter object and redraw.