Covering 2D plots with 3D surface in python

Question

I am attempting to take many xz plots, each at various y values, and overlay a surface. I have seen many examples of how to plot 3D surfaces in python, but aside from this post, nothing seems to match my inquiry very closely.

The image of what I need to do is shown below (Note: ignore the "constant x" - this is due to a more complicated variable layout than I explained here):

My code is as follows, and simply takes data and plots each of the individual Magnitude vs. Frequency plots (xz plots):

import numpy as np
import glob, os
import codecs
import re
import matplotlib.pyplot as plt
#-------------------------------------------------------------------------                   
os.chdir('C:/Users/elarrick/Desktop/201807161056')
dataFolders = glob.glob('./*.ltda')

dataLines = []
freq = []
OpenLoopMag = []
OpenLoopPhase = []
for item in dataFolders:
    name, ext = os.path.splitext(item)
    if ext == '.ltda':
        print item
        dataLines = []
        f = codecs.open(item, encoding='utf-8')
        for line in f:
            if '<p>' in line:
                dataLines.append(line)      #All lines with <p> are an entry in dataLines
        #print "\n\n", dataLines
        #break
        for item in dataLines:
            item = re.sub("<p>", "", item)
            item = re.sub("True</p>", "", item)
            item = item.replace(",", "")
            splitItem = item.split()
            #print splitItem
            freq.append(float(splitItem[0]))
            OpenLoopMag.append(float(splitItem[1]))
            OpenLoopPhase.append(float(splitItem[2]))
        print "Frequencies: ", freq
        print "\n\n\n\n\n\nOpenLoopMag: ", OpenLoopMag
#   This is where I will make the plots for each x,y position
        name = name.strip(".\\")
        name = name.replace("-","NEG")
        plt.semilogx(freq, OpenLoopMag)
        #plt.plot(freq, OpenLoopMag)
        plt.xlabel("Frequency, (Hz)")
        plt.ylabel("Magnitude")
        plt.title("{0}".format(name))
        plt.xlim([20,2000])
        #plt.ylim([-43.2,10.9])
        ticks = [20,40,70,100,200,400,700,1000,2000]
        plt.xticks(ticks,ticks)
        plt.savefig("plot_{0}.png".format(name))

#________ Clear the values for the next data folder_______#            
        freq = []
        OpenLoopMag = []
        OpenLoopPhase = []
        break
    else:
        print "Something went wrong - check ColorMap.py"
        sys.exit()

The next thing I need is to grab each plot, find the y value at which the data was taken, and plot along a y axis (shown coming out of the page in the previous picture). Can you help me do that?

Answer 1

Here is an example that resembles your drawing quite well.

from mpl_toolkits.mplot3d import Axes3D
from matplotlib.collections import PolyCollection
import matplotlib.pyplot as plt
import numpy as np

# Generate test data
Ny,Nx = 100,100
x = np.linspace(0,1,Nx)
y = np.linspace(0,1,Ny)
x,y = np.meshgrid(x,y)
z = (1 - x**2) * y**.5

# Indices for the y-slices and corresponding slice positions along y-axis
slice_i = [20, 40, 60, 80]
slice_pos = np.array(slice_i) / Ny

def polygon_under_graph(x, y):
    '''
    Construct the vertex list which defines the polygon filling the space under
    the (x, y) line graph.  Assumes the xlist are in ascending order.
    '''
    return [(x[0], 0.)] + list(zip(x, y)) + [(x[-1], 0.)]

fig = plt.figure()
ax = fig.gca(projection='3d')

verts = []
for i in slice_i:
    verts.append(polygon_under_graph(x[i], z[i]))

poly = PolyCollection(verts, facecolors='gray', edgecolors='k')

# add slices to 3d plot
ax.add_collection3d(poly, zs=slice_pos, zdir='y')

# plot surface between first and last slice as a mesh
ax.plot_surface(x[slice_i[0]:slice_i[-1]], 
                y[slice_i[0]:slice_i[-1]],
                z[slice_i[0]:slice_i[-1]], 
                rstride=10, cstride=10, alpha=0, edgecolors='k')

ax.set_xlabel('X')
ax.set_ylabel('Y')
ax.set_zlabel('Z')

plt.show()

See result: