I'm trying to generate random sample points on a cartesian plane using polar coordinates. I have a cartesian map with polar sectors, I'd like to put a random sample point within each of the sectors.
Problem Visual Description
I've added a sample point in the first sector. The problem is I don't know how to set the min and max limits for each sector as it's a cartesian plane (using cartesian min and max of the sector corners will give you boxes instead of the entire polar sector).
Code is commented for clarity. Final output posted below.
import numpy as np
import matplotlib.pyplot as plt
plt.rcParams['figure.figsize'] = [10, 10]
import math
import pylab as pl
from matplotlib import collections as mc
import pprint
from IPython.utils import io
from random import randrange, uniform
#convertes cartesian x,y coordinates to polar r, theta coordinates
def cart2pol(x, y):
rho = np.sqrt(x**2 + y**2)
phi = np.arctan2(y, x)
return np.array([rho, phi])
#convertes polar r,theta coordinates to cartesian x,y coordinates
def pol2cart(r, theta): #r is distance
x = r * np.cos(theta)
y = r * np.sin(theta)
return np.array([x, y])
#cooks delicious pie
pi = np.pi
#no idea what this does
theta = np.linspace(0,2*pi,100)
#x theta
def x_size(r):
return r*np.cos(theta)
#y theta
def y_size(r):
return r*np.sin(theta)
#calculates distribution of sectors on a circle in radians
#eg. sub_liner(3) = array([0. , 2.0943951, 4.1887902])
def sub_liner(k):
sub_lines = []
for c,b in enumerate(range(0,k)):
sub_lines = np.append(sub_lines,((12*pi/6)/k)*c)
return sub_lines
#calculates all distribution sectors for every ring and puts them in a list
def mlp(i):
master_lines = []
k = 3
for a in range(0,i):
master_lines.append(sub_liner(k))
k += 3
return master_lines
#calculates all four corners of each sector for a ring
#(ring,ring points,number of rings)
def cg(r,rp,n):
return [[[pol2cart(r-1,mlp(n)[r-1][i])[0],pol2cart(r-1,mlp(n)[r-1][i])[1]]\
,[pol2cart(r,mlp(n)[r-1][i])[0],pol2cart(r,mlp(n)[r-1][i])[1]]] for i in range(0,rp)]
#generates all corners for the ring sectors
def rg(n):
cgl = []
k = 3
for r in range(1,11):
cgl.append(cg(r,k,n))
k += 3
output = cgl[0]
for q in range(1,10):
output = np.concatenate((output,cgl[q]))
return output
#print(cg(1,3,10)[0][0][0])
#print(cg(1,3,10))
# randrange gives you an integral value
irand = randrange(0, 10)
# uniform gives you a floating-point value
frand = uniform(0, 10)
#define ring sectors
ring_sectors = rg(10)
#define node points
nx = 0.5
ny = 0.5
#define ring distance
ymin = [0]
ymax = [1]
#generate rings
ring_r = np.sqrt(1.0)
master_array = np.array([[x_size(i),y_size(i)] for i in range(0,11)])
#plot rings
fig, ax = plt.subplots(1)
[ax.plot(master_array[i][0],master_array[i][1]) for i in range(0,11)]
ax.set_aspect(1)
size = 10
plt.xlim(-size,size)
plt.ylim(-size,size)
#generate nodes
ax.plot(nx, ny, 'o', color='black');
#ring lines
lc = mc.LineCollection(ring_sectors, color='black', linewidths=2)
ax.add_collection(lc)
plt.grid(linestyle='--')
plt.title('System Generator', fontsize=8)
plt.show()
Sample output can be viewed at.
Edit:
What I've tried:
Based on feedback, I implemented a system which gets random uniform values between the polar coordinates, and it works, but the points aren't neatly distributed within their sectors as they should be, and I'm not sure why. Maybe my math is off or I made a mistake in the generator functions. If anyone has any insight, I'm all ears.
Output with points
def ngx(n):
rmin = 0
rmax = 1
nxl = []
s1 = 0
s2 = 1
k = 0
for i in range(0,n):
for a in range(0,rmax*3):
nxl.append(pol2cart(np.random.uniform(rmin,rmax),\
np.random.uniform(sub_liner(rmax*3)[(s1+k)%(rmax*3)],sub_liner(rmax*3)[(s2+k)%(rmax*3)]))[0])
k += 1
rmin += 1
rmax += 1
return nxl
def ngy(n):
rmin = 0
rmax = 1
nyl = []
s1 = 0
s2 = 1
k = 0
for i in range(0,n):
for a in range(0,rmax*3):
nyl.append(pol2cart(np.random.uniform(rmin,rmax),\
np.random.uniform(sub_liner(rmax*3)[(s1+k)%(rmax*3)],sub_liner(rmax*3)[(s2+k)%(rmax*3)]))[1])
k += 1
rmin += 1
rmax += 1
return nyl
#define node points
nx = ngx(10)
ny = ngy(10)
Related
I want to generate random points in a box (a=0.2m, b=0.2m, c=1m). This points should have random distance between each other but minimum distance between two points is should be 0.03m, for this I used random.choice. When I run my code it generates random points but distance management is so wrong. Also my float converting approximation is terrible because I don't want to change random values which I generate before but I couldn't find any other solution. I'm open to suggestions.
Images
graph1
graph2
import random
import matplotlib.pyplot as plt
# BOX a = 0.2m b=0.2m h=1m
save = 0 #for saving 3 different plot.
for k in range(3):
pointsX = [] #information of x coordinates of points
pointsY = [] #information of y coordinates of points
pointsZ = [] #information of z coordinates of points
for i in range(100): #number of the points
a = random.uniform(0.0,0.00001) #for the numbers generated below are float.
x = random.choice(range(3, 21,3)) #random coordinates for x
x1 = x/100 + a
pointsX.append(x1)
y = random.choice(range(3, 21,3)) #random coordinates for y
y1 = y/100 + a
pointsY.append(y1)
z = random.choice(range(3, 98,3)) #random coordinates for z
z1 = z/100 + a
pointsZ.append(z1)
new_pointsX = list(set(pointsX)) # deleting if there is a duplicates
new_pointsY = list(set(pointsY))
new_pointsZ = list(set(pointsZ))
# i wonder max and min values it is or not between borders.
print("X-Min", min(new_pointsX))
print("X-Max", max(new_pointsX))
print("Y-Min", min(new_pointsY))
print("Y-Max", max(new_pointsY))
print("Z-Min", min(new_pointsZ))
print("Z-Max", max(new_pointsZ))
if max(new_pointsX) >= 0.2 or max(new_pointsY) >= 0.2:
print("MAX VALUE GREATER THAN 0.2")
if max(new_pointsZ) >= 0.97:
print("MAX VALUE GREATER THAN 0.97")
#3D graph
fig = plt.figure(figsize=(18,9))
ax = plt.axes(projection='3d')
ax.set_xlim([0, 0.2])
ax.set_ylim([0, 0.2])
ax.set_zlim([0, 1])
ax.set_title('title',fontsize=18)
ax.set_xlabel('X',fontsize=14)
ax.set_ylabel('Y',fontsize=14)
ax.set_zlabel('Z',fontsize=14)
ax.scatter3D(new_pointsX, new_pointsY, new_pointsZ);
save += 1
plt.savefig("graph" + str(save) + ".png", dpi=900)
As mentioned in the comments by #user3431635, you can check each point with all previous points before appending that new point to the list. I would do that something like this:
import random
import numpy as np
import matplotlib.pyplot as plt
plt.close("all")
a = 0.2 # x bound
b = 0.2 # y bound
c = 1.0 # z bound
N = 1000 # number of points
def distance(p, points, min_distance):
"""
Determines if any points in the list are less than the minimum specified
distance apart.
Parameters
----------
p : tuple
`(x,y,z)` point.
points : ndarray
Array of points to check against. `x, y, z` points are columnwise.
min_distance : float
Minimum allowable distance between any two points.
Returns
-------
bool
True if point `p` is at least `min_distance` from all points in `points`.
"""
distances = np.sqrt(np.sum((p+points)**2, axis=1))
distances = np.where(distances < min_distance)
return distances[0].size < 1
points = np.array([]) # x, y, z columnwise
while points.shape[0] < 1000:
x = random.choice(np.linspace(0, a, 100000))
y = random.choice(np.linspace(0, b, 100000))
z = random.choice(np.linspace(0, c, 100000))
p = (x,y,z)
if len(points) == 0: # add first point blindly
points = np.array([p])
elif distance(p, points, 0.03): # ensure the minimum distance is met
points = np.vstack((points, p))
fig = plt.figure(figsize=(18,9))
ax = plt.axes(projection='3d')
ax.set_xlim([0, a])
ax.set_ylim([0, b])
ax.set_zlim([0, c])
ax.set_title('title',fontsize=18)
ax.set_xlabel('X',fontsize=14)
ax.set_ylabel('Y',fontsize=14)
ax.set_zlabel('Z',fontsize=14)
ax.scatter(points[:,0], points[:,1], points[:,2])
Note, this might not be the randomness you're looking for. I have written it to take the range of x, y, and z values and split it into 100000 increments; a new x, y, or z point is then chosen from those values.
I'm trying to calculate the mean value of a quantity(in the form of a 2D array) as a function of its distance from the center of a 2D grid. I understand that the idea is that I identify all the array elements that are at a distance R from the center, and then add them up and divide by the number of elements. However, I'm having trouble actually identifying an algorithm to go about doing this.
I have attached a working example of the code to generate the 2d array below. The code is for calculating some quantities that are resultant from gravitational lensing, so the way the array is made is irrelevant to this problem, but I have attached the entire code so that you could create the output array for testing.
import numpy as np
import multiprocessing
import matplotlib.pyplot as plt
n = 100 # grid size
c = 3e8
G = 6.67e-11
M_sun = 1.989e30
pc = 3.086e16 # parsec
Dds = 625e6*pc
Ds = 1726e6*pc #z=2
Dd = 1651e6*pc #z=1
FOV_arcsec = 0.0001
FOV_arcmin = FOV_arcsec/60.
pix2rad = ((FOV_arcmin/60.)/float(n))*np.pi/180.
rad2pix = 1./pix2rad
Renorm = (4*G*M_sun/c**2)*(Dds/(Dd*Ds))
#stretch = [10, 2]
# To create a random distribution of points
def randdist(PDF, x, n):
#Create a distribution following PDF(x). PDF and x
#must be of the same length. n is the number of samples
fp = np.random.rand(n,)
CDF = np.cumsum(PDF)
return np.interp(fp, CDF, x)
def get_alpha(args):
zeta_list_part, M_list_part, X, Y = args
alpha_x = 0
alpha_y = 0
for key in range(len(M_list_part)):
z_m_z_x = (X - zeta_list_part[key][0])*pix2rad
z_m_z_y = (Y - zeta_list_part[key][1])*pix2rad
alpha_x += M_list_part[key] * z_m_z_x / (z_m_z_x**2 + z_m_z_y**2)
alpha_y += M_list_part[key] * z_m_z_y / (z_m_z_x**2 + z_m_z_y**2)
return (alpha_x, alpha_y)
if __name__ == '__main__':
# number of processes, scale accordingly
num_processes = 1 # Number of CPUs to be used
pool = multiprocessing.Pool(processes=num_processes)
num = 100 # The number of points/microlenses
r = np.linspace(-n, n, n)
PDF = np.abs(1/r)
PDF = PDF/np.sum(PDF) # PDF should be normalized
R = randdist(PDF, r, num)
Theta = 2*np.pi*np.random.rand(num,)
x1= [R[k]*np.cos(Theta[k])*1 for k in range(num)]
y1 = [R[k]*np.sin(Theta[k])*1 for k in range(num)]
# Uniform distribution
#R = np.random.uniform(-n,n,num)
#x1= np.random.uniform(-n,n,num)
#y1 = np.random.uniform(-n,n,num)
zeta_list = np.column_stack((np.array(x1), np.array(y1))) # List of coordinates for the microlenses
x = np.linspace(-n,n,n)
y = np.linspace(-n,n,n)
X, Y = np.meshgrid(x,y)
M_list = np.array([0.1 for i in range(num)])
# split zeta_list, M_list, X, and Y
zeta_list_split = np.array_split(zeta_list, num_processes, axis=0)
M_list_split = np.array_split(M_list, num_processes)
X_list = [X for e in range(num_processes)]
Y_list = [Y for e in range(num_processes)]
alpha_list = pool.map(
get_alpha, zip(zeta_list_split, M_list_split, X_list, Y_list))
alpha_x = 0
alpha_y = 0
for e in alpha_list:
alpha_x += e[0]
alpha_y += e[1]
alpha_x_y = 0
alpha_x_x = 0
alpha_y_y = 0
alpha_y_x = 0
alpha_x_y, alpha_x_x = np.gradient(alpha_x*rad2pix*Renorm,edge_order=2)
alpha_y_y, alpha_y_x = np.gradient(alpha_y*rad2pix*Renorm,edge_order=2)
det_A = 1 - alpha_y_y - alpha_x_x + (alpha_x_x)*(alpha_y_y) - (alpha_x_y)*(alpha_y_x)
abs = np.absolute(det_A)
I = abs**(-1.)
O = np.log10(I+1)
plt.contourf(X,Y,O,100)
The array of interest is O, and I have attached a plot of how it should look like. It can be different based on the random distribution of points.
What I'm trying to do is to plot the mean values of O as a function of radius from the center of the grid. In the end, I want to be able to plot the average O as a function of distance from center in a 2d line graph. So I suppose the first step is to define circles of radius R, based on X and Y.
def circle(x,y):
r = np.sqrt(x**2 + y**2)
return r
Now I just have to figure out a way to find all the values of O, that have the same indices as equivalent values of R. Kinda confused on this part and would appreciate any help.
You can find the geometric coordinates of a circle with center (0,0) and radius R as such:
phi = np.linspace(0, 1, 50)
x = R*np.cos(2*np.pi*phi)
y = R*np.sin(2*np.pi*phi)
these values however will not fall on the regular pixel grid but in between.
In order to use them as sampling points you can either round the values and use them as indexes or interpolate the values from the near pixels.
Attention: The pixel indexes and the x, y are not the same. In your example (0,0) is at the picture location (50,50).
Assume that you have an NxM matrix, with values ranging from [0,100]. What I'd like to do is place points with a density (inversely) relative to the values in that area.
For example, here's a 2D Gaussian field, inverted s.t. the centroid has a value of 0, and the perimeter is at 100:
I'd like to pack the points so that they appear somewhat similar to this image:
Note how there is a radial spread outwards.
My attempt looks a little different :( ...
What I attempt to do is (i) generate a boolean area, of the same shape and size, and (ii) move through the rows and columns. If the value of the boolean array at some point is True, then pass; otherwise, add a [row,col] point to a list and cover the boolean array with True in a radius proportional to the value in the Gaussian array.
The choice of Gaussian for this example isn't important, the fundamental idea is that: given a floating point matrix, how can one place points with a density proportional to those values?
Any help very much appreciated :)
import matplotlib.pyplot as plt
import numpy as np
from math import exp
def gaussian(x,y,x0,y0,A=10.0,sigma_x=10.0,sigma_y=10.0):
return A - A*exp(-((x-x0)**2/(2*sigma_x**2) + (y-y0)**2/(2*sigma_y**2)))
def generate_grid(width=100,height=100):
grid = np.empty((width,height))
for x in range(0,width):
for y in range(0,height):
grid[x][y] = gaussian(x,y,width/2,height/2,A=100.0)
return grid
def cover_array(a,row,col,radius):
nRows = np.shape(grid)[0]
nCols = np.shape(grid)[1]
mid = round(radius / 2)
half_radius = int(round(radius))
for x in range(-half_radius,half_radius):
for y in range(-half_radius,half_radius):
if row+x >= 0 and x+row < nRows and col+y >= 0 and y+col < nCols:
if (x-mid)**2 + (y-mid)**2 <= radius**2:
a[row+x][col+y] = True
def pack_points(grid):
points = []
nRows = np.shape(grid)[0]
nCols = np.shape(grid)[1]
maxDist = 50.0
minDist = 0.0
maxEdge = 10.0
minEdge = 5.0
grid_min = 0.0
grid_max = 100.0
row = 0
col = 0
arrayCovered = np.zeros((nRows,nCols))
while True:
if row >= nRows:
return np.array(points)
if arrayCovered[row][col] == False:
radius = maxEdge * ((grid[row][col] - grid_min) / (grid_max - grid_min))
cover_array(arrayCovered,row,col,radius)
points.append([row,col])
col += 1
if col >= nCols:
row += 1
col = 0
grid = generate_grid()
plt.imshow(grid)
plt.show()
points = pack_points(grid)
plt.scatter(points[:,0],points[:,1])
plt.show()
Here is a cheap and simple method, although it requires hand-setting an amount parameter:
import numpy as np
import matplotlib.pyplot as plt
def gaussian(x,y,x0,y0,A=10.0,sigma_x=10.0,sigma_y=10.0):
return A - A*np.exp(-((x-x0)**2/(2*sigma_x**2) + (y-y0)**2/(2*sigma_y**2)))
def distribute_points(data, amount=1):
p = amount * (1 / data)
r = np.random.random(p.shape)
return np.where(p > r)
ii, jj = np.mgrid[-10:10:.1, -10:10:.1]
data = gaussian(ii, jj, 0, 0)
px, py = distribute_points(data, amount=.03)
plt.imshow(data)
plt.scatter(px, py, marker='.', c='#ff000080')
plt.xticks([])
plt.yticks([])
plt.xlim([0, len(ii)])
plt.ylim([0, len(jj)])
Result:
I am trying to map surface curvature (mean, gaussian and principle curvature) values to surface faces. I have computed the curvature values for an artificially generated 3D surface (eg. cylinder). The resulting 3D surface that I am trying to get is something like this mean curvature mapped to surface. Can somebody guide me in how to get this?
The code for the surface I am creating is:
import math
import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
xindex = []
yindex = []
zindex = []
x = []
y = []
z = []
count = 1
surfaceSt = []
import numpy
numpy.set_printoptions(threshold=numpy.nan)
#surfaceStX = numpy.empty((10,36))
#surfaceStY = numpy.empty((10,36))
#surfaceStZ = numpy.empty((10,36))
surfaceStZ = []
surfaceStX = []
surfaceStY = []
for i in range(1,21):
if i < 11:
x = []
y = []
z = []
pt = []
ptX = []
ptY = []
ptZ = []
for t in range(0,360,10):
x = i*math.sin(math.radians(t))
y = i*math.cos(math.radians(t))
z = i-1
ptX.append(x)
ptY.append(y)
ptZ.append(z)
pt.append([x,y,z])
ptX.append(ptX[0])
ptY.append(ptY[0])
ptZ.append(ptZ[0])
surfaceStX.append(ptX)
surfaceStY.append(ptY)
surfaceStZ.append(ptZ)
# numpy.append(surfaceStX,ptX)
# numpy.append(surfaceStY,ptY)
# numpy.append(surfaceStZ,ptZ)
#ax.scatter(x,y,z)
elif i >= 11:
x = []
y = []
z = []
pt = []
ptX = []
ptY = []
ptZ = []
for t in range(0,360,10):
x = (i-count)*math.sin(math.radians(t))
y = (i-count)*math.cos(math.radians(t))
z = i-1
ptX.append(x)
ptY.append(y)
ptZ.append(z)
pt.append([x,y,z])
ptX.append(ptX[0])
ptY.append(ptY[0])
ptZ.append(ptZ[0])
surfaceStX.append(ptX)
surfaceStY.append(ptY)
surfaceStZ.append(ptZ)
count +=2
X = numpy.array(surfaceStX)
Y = numpy.array(surfaceStY)
Z = numpy.array(surfaceStZ)
ax = fig.add_subplot(111, projection='3d')
ax.plot_surface(X, Y, Z, rstride=1, cstride=1,shade = 'True' )
from surfaceCurvature import surface_curvature
Pcurvature,Gcurvature,Mcurvature = surface_curvature(X,Y,Z)
plt.show()
My surface curvature computation is given below (courtesy: https://github.com/sujithTSR/surface-curvature):
def surface_curvature(X,Y,Z):
(lr,lb)=X.shape
#print lr
#print "awfshss-------------"
#print lb
#First Derivatives
Xv,Xu=np.gradient(X)
Yv,Yu=np.gradient(Y)
Zv,Zu=np.gradient(Z)
#Second Derivatives
Xuv,Xuu=np.gradient(Xu)
Yuv,Yuu=np.gradient(Yu)
Zuv,Zuu=np.gradient(Zu)
Xvv,Xuv=np.gradient(Xv)
Yvv,Yuv=np.gradient(Yv)
Zvv,Zuv=np.gradient(Zv)
#2D to 1D conversion
#Reshape to 1D vectors
Xu=np.reshape(Xu,lr*lb)
Yu=np.reshape(Yu,lr*lb)
Zu=np.reshape(Zu,lr*lb)
Xv=np.reshape(Xv,lr*lb)
Yv=np.reshape(Yv,lr*lb)
Zv=np.reshape(Zv,lr*lb)
Xuu=np.reshape(Xuu,lr*lb)
Yuu=np.reshape(Yuu,lr*lb)
Zuu=np.reshape(Zuu,lr*lb)
Xuv=np.reshape(Xuv,lr*lb)
Yuv=np.reshape(Yuv,lr*lb)
Zuv=np.reshape(Zuv,lr*lb)
Xvv=np.reshape(Xvv,lr*lb)
Yvv=np.reshape(Yvv,lr*lb)
Zvv=np.reshape(Zvv,lr*lb)
Xu=np.c_[Xu, Yu, Zu]
Xv=np.c_[Xv, Yv, Zv]
Xuu=np.c_[Xuu, Yuu, Zuu]
Xuv=np.c_[Xuv, Yuv, Zuv]
Xvv=np.c_[Xvv, Yvv, Zvv]
# First fundamental Coeffecients of the surface (E,F,G)
E=np.einsum('ij,ij->i', Xu, Xu)
F=np.einsum('ij,ij->i', Xu, Xv)
G=np.einsum('ij,ij->i', Xv, Xv)
m=np.cross(Xu,Xv,axisa=1, axisb=1)
p=np.sqrt(np.einsum('ij,ij->i', m, m))
n=m/np.c_[p,p,p]
# Second fundamental Coeffecients of the surface (L,M,N), (e,f,g)
L= np.einsum('ij,ij->i', Xuu, n) #e
M= np.einsum('ij,ij->i', Xuv, n) #f
N= np.einsum('ij,ij->i', Xvv, n) #g
# Gaussian Curvature
K=(L*N-M**2)/(E*G-F**2)
K=np.reshape(K,lr*lb)
# Mean Curvature
H = (E*N + G*L - 2*F*M)/((E*G - F**2))
H = np.reshape(H,lr*lb)
# Principle Curvatures
Pmax = H + np.sqrt(H**2 - K)
Pmin = H - np.sqrt(H**2 - K)
#[Pmax, Pmin]
Principle = [Pmax,Pmin]
return Principle,K,H
EDIT 1:
I tried a few things based on the link provided by armatita. Following is my code:
'''
Creat half cylinder
'''
import numpy
import matplotlib.pyplot as plt
import math
ptX= []
ptY = []
ptZ = []
ptX1 = []
ptY1 = []
ptZ1 = []
for i in range(0,10):
x = []
y = []
z = []
for t in range(0,200,20):
x.append(10*math.cos(math.radians(t)))
y.append(10*math.sin(math.radians(t)))
z.append(i)
x1= 5*math.cos(math.radians(t))
y1 = 5*math.sin(math.radians(t))
z1 = i
ptX1.append(x1)
ptY1.append(y1)
ptZ1.append(z1)
ptX.append(x)
ptY.append(y)
ptZ.append(z)
X = numpy.array(ptX)
Y = numpy.array(ptY)
Z = numpy.array(ptZ)
fig = plt.figure()
ax = fig.add_subplot(111,projection = '3d')
from surfaceCurvature import surface_curvature
p,g,m= surface_curvature(X,Y,Z)
n = numpy.reshape(m,numpy.shape(X))
ax.plot_surface(X,Y,Z, rstride=1, cstride=1)
plt.show()
'''
Map mean curvature to color
'''
import numpy as np
X1 = X.ravel()
Y1 = Y.ravel()
Z1 = Z.ravel()
from scipy.interpolate import RectBivariateSpline
# Define the points at the centers of the faces:
y_coords, x_coords = np.unique(Y1), np.unique(X1)
y_centers, x_centers = [ arr[:-1] + np.diff(arr)/2 for arr in (y_coords, x_coords)]
# Convert back to a 2D grid, required for plot_surface:
#Y1 = Y.reshape(y_coords.size, -1)
#X1 = X.reshape(-1, x_coords.size)
#Z1 = Z.reshape(X.shape)
C = m.reshape(X.shape)
C -= C.min()
C /= C.max()
interp_func = RectBivariateSpline(x_coords, y_coords, C.T, kx=1, ky=1)
I get the following error:
raise TypeError('y dimension of z must have same number of y')
TypeError: y dimension of z must have same number of elements as y
All the dimensions are same. Can anybody tell what's going wrong with my implementation?
I think you need to figure out exactly what you need. Looking at your code I notice you are producing variables that have no use. Also you seem to have a function to calculate the surface curvature but than you try to make some calculations using the np.unique function for which I cannot see the purpose here (and that is why that error appears).
So let's assume this:
You have a function that returns the curvature value for each cell.
You have the X,Y and Z meshes to plot that surface.
Using your code, and assuming you m variable is the curvature (again this is in your code), if I do this:
import numpy
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D
from matplotlib import cm
import math
# Here would be the surface_curvature function
X = numpy.array(ptX)
Y = numpy.array(ptY)
Z = numpy.array(ptZ)
p,g,m= surface_curvature(X,Y,Z)
C = m.reshape(X.shape)
C -= C.min()
C /= C.max()
fig = plt.figure()
ax = fig.add_subplot(111,projection = '3d')
n = numpy.reshape(m,numpy.shape(X))
ax.plot_surface(X,Y,Z,facecolors = cm.jet(C), rstride=1, cstride=1)
plt.show()
, I obtain this:
Which is a value mapped to color in a matplotlib surface. If that C you've built is not the actual curvature you need to replace it by the one that is.
I am attempting to plot a distribution:
This is the temperature distribution inside of a sphere of radius (a) whose upper hemisphere is held at T=1 and lower hemisphere is held at T=0 (ignore the discontinuity at the boundary between the two hemispheres) and P_l are the Legendre polynomials of the first kind.
import pylab as pl
from scipy.special import eval_legendre as Leg
import math,sys
def sumTerm(a,r,theta,l):
"""
Compute term of sum given radius of sphere (a),
y and z coordinates, and the current index of the
Legendre polynomials (l) over the entire range
where these polynomials are orthogonal [-1,1].
"""
xRange = pl.arange(-0.99,1.0,0.01)
x = pl.cos(theta)
# correct for scipy handling negative indices incorrectly
lLow = l-1
lHigh = l+1
if lLow < 0:
lLow = -lLow-1
return 0.5*((r/a)**l)*Leg(l,x)*(Leg(lLow,0)-Leg(lHigh,0))
def main():
n = 10 # number of l terms to expand to
a = 1.0 # radius of sphere
# generate r, theta values
aBins = pl.linspace(0, 2*pl.pi, 360) # 0 to 360 in steps of 360/N.
rBins = pl.linspace(0, 1, 50)
theta,r = pl.meshgrid(aBins, rBins)
tempProfile = pl.zeros([50,360])
for nr,ri in enumerate(rBins):
for nt,ti in enumerate(aBins):
temp = 0.0
for l in range(n):
temp += sumTerm(a, ri, ti, l)
tempProfile[nr,nt] = temp
# plot the Temperature profile
pl.imshow(tempProfile)
pl.colorbar()
pl.axes().set_aspect('equal')
pl.show()
if __name__=='__main__':
main()
This yields the following plot:
This looks good, but how can I display this in polar coordinates?
Ok, so I figured it out. Here is my solution (I feel strange giving my own solution to this).
# =============================================================================
# Plot central cross-section of sphere under steady-state conditions
# where the temperature on upper hemisphere is T=T_0 and the lower
# hemisphere is held at T=0. This is an expansion in Legendre polynomials.
#
# Author: Max Graves
# Last Revised: 8-OCT-2013
# =============================================================================
import pylab as pl
from scipy.special import eval_legendre as Leg
import math,sys
def sumTerm(a,r,theta,l):
"""
Compute term of sum given radius of sphere (a),
y and z coordinates, and the current index of the
Legendre polynomials (l) over the entire range
where these polynomials are orthogonal [-1,1].
"""
xRange = pl.arange(-0.99,1.0,0.01)
x = pl.cos(theta)
# correct for scipy handling negative indices incorrectly
lLow = l-1
lHigh = l+1
if lLow < 0:
lLow = -lLow-1
return 0.5*((r/a)**l)*Leg(l,x)*(Leg(lLow,0)-Leg(lHigh,0))
def main():
n = 20 # number of l terms to expand to
a = 1.0 # radius of sphere
# generate r, theta values
aBins = pl.linspace(0, 2*pl.pi, 360) # 0 to 360 in steps of 360/N.
rBins = pl.linspace(0, 1, 50)
theta,r = pl.meshgrid(aBins, rBins)
tempProfile = pl.zeros([50,360])
for nr,ri in enumerate(rBins):
print nr
for nt,ti in enumerate(aBins):
temp = 0.0
for l in range(n):
temp += sumTerm(a, ri, ti, l)
tempProfile[nr,nt] = temp
# plot the Temperature profile
fig, ax = pl.subplots(subplot_kw=dict(projection='polar'))
pax = ax.pcolormesh(theta, r, tempProfile)
ax.set_theta_zero_location("N") # 'north' location for theta=0
ax.set_theta_direction(-1) # angles increase clockwise
fig.colorbar(pax)
pl.show()
if __name__=='__main__':
main()
which yields the following plot: