matlab code for python script?

i am trying to write a matlab code for python script as:

class structure:

def __init__(self, shape, eps, mu):

self.shape = shape

self.eps = eps

self.mu = mu

self.epsr = np.ones(shape, dtype='float64')

self.mur = np.ones(shape, dtype='float64')

class Sphere(structure):

def __init__(self, shape, center, R, eps, mu, smoothing = False):

super(Sphere, self).__init__(shape, eps, mu)

self.center = center

self.R = R

self.smoothing = smoothing

self.get_epsr()

def get_epsr(self):

x = np.arange(self.shape[0])

y = np.arange(self.shape[1])

z = np.arange(self.shape[2])

X,Y,Z = np.meshgrid(x,y,z)

self.r = np.sqrt((self.center[1]-X)**2 + (self.center[0]-Y)**2 + (self.center[2]-Z)**2)

self.region = np.where(self.r >= self.R, 0, 1)

print("self.region value: ",self.region)

print("self.region shape: ",self.region.shape)

self.epsr += self.region * (self.eps - 1)

if self.smoothing == True:

smoothing_region = 1 - (np.where((0 < (self.r - self.R)) & ((self.r - self.R) < 1), 1/3*(self.r+np.sqrt(self.r**2-1)-2*self.R)**2, 1))

self.epsr += smoothing_region * (self.eps - 1)

del self.r

the call for these structures in python is as:

um = 1e-6

dx = 4.8 * um

lamb = 74.9*um

eps = np.zeros((250,250))

str1 = Sphere(shape = (250,250,250), center = (125,125,125), R = lamb*3/dx, eps=10, mu=1)

THE MATLAB SCRIPT WHICH I TRIED IS AS:

shape = [250,250,250]
N1=shape(1);
N2=shape(2);
N3=shape(3);

um = 1e-6
c = 3e8                        % m/s
dx = 4.8 * um
dy = 4.8 * um
dz = 4.8 * um
dt = 1/4 * dx / c
lamb = 74.9*um
R = lamb*3/dx; 
eps=10; 
mu=1;


x = linspace(0,N1-1,N1);
y = linspace(0,N2-1,N2);
z = linspace(0,N3-1,N3);

[X,Y,Z] = meshgrid(x,y,z);
X=(X(:))';
Y=(Y(:))';
Z=(Z(:))';

center = [125, 125,125];
r = sqrt((center(2)-X).^2 + (center(1)-Y).^2 + (center(3)-Z).^2);

epsr = ones(shape);
mur  = ones(shape);    

for k=1:1:length(r)
    for j = 1:1:length(r)
        for k=1:1:length(r)
            if r(:,:,k) >= R
                epsr(:,:,k) = 

Q: i am struck with implementation of region in matlab, can someone help me with this

Answer 1

[Paras Gupta]

Hi Asim,

I understand that you want to convert the given python code to MATLAB.

In the given Python code, the “region” variable is calculated using np.where(self.r >= self.R, 0, 1). This condition sets the value of region to 0 where self.r >= self.R and 1 otherwise.

To implement this in MATLAB, you can use logical indexing as shown below:

shape = [250,250,250];
N1=shape(1);
N2=shape(2);
N3=shape(3);

um = 1e-6;
c = 3e8;                     % m/s
dx = 4.8 * um;
dy = 4.8 * um;
dz = 4.8 * um;
dt = 1/4 * dx / c;
lamb = 74.9*um;
R = lamb*3/dx; 
eps=10; 
mu=1;


x = linspace(0,N1-1,N1);
y = linspace(0,N2-1,N2);
z = linspace(0,N3-1,N3);

[X,Y,Z] = meshgrid(x,y,z);
% X=(X(:))';
% Y=(Y(:))';
% Z=(Z(:))';

center = [125, 125,125];
r = sqrt((center(2)-X).^2 + (center(1)-Y).^2 + (center(3)-Z).^2);

epsr = ones(shape);
mur  = ones(shape);    

region = zeros(size(r));
region(r >= R) = 0;
region(r < R) = 1;
epsr = ones(shape);
epsr = epsr + region * (eps - 1);

smoothing = false;
% Calculate smoothing_region
smoothing_region = zeros(size(r));
if smoothing==true
    temp = (0 < (r - R)) & ((r - R) < 1);
    smoothing_region(temp) = 1/3 * (r(temp) + sqrt(r(temp).^2 - 1) - 2 * R).^2;
end

% Update epsr with smoothing_region
epsr = epsr + smoothing_region * (eps - 1);

You can refer to the following documentation on array indexing for more information on the use of logical indexing.

https://www.mathworks.com/help/matlab/math/array-indexing.html

Hope this helps.