Matlab code for Engineering Physics not working

CODE

%Assigning values of required constants
k=1/(4*pi*8.542e-12) ;
z=linspace(-0.5,0.5) ;
E=zeros(size(z));
Q=1e-10;

%Creating a matrix containing position vectors for the 100 points on the z-axis
rz=linspace(-0.5,0.5) ;
rx=zeros(size(rz)) ;
ry=zeros(size(rz)) ;
r=[rx ; ry ; rz] ;

%Assigning variables to the position vectors
syms x [100 1]
for i=1 : 100
     x(i)=transpose(r(: , i)) ;
end

%Creating a matrix containing position vectors for the 100 points on the y-axis
r1y=linspace(-0.5,0.5) ;
r1z=zeros(size(r1y)) ;
r1x=zeros(size(r1y)) ;
r1=[r1x ; r1y ; r1z] ;

%Assigning variables to the position vectors
syms x1 [100 1]
for i=1 : 100
x1(i)=transpose(r1(: , i)) ;
end

%Calculating distance between the points on z-axis and y-axis
for m=1 : 100
     xi(m)=norm(x(m) - x1(m)) ;
end
E=zeros(z) ;
for m=1:100
       E(m)=k*Q / abs(xi(m)) ^ 2 ;
end

%Analytical calculation and plotting graph of the solution
cons=1/(2*pi*8.542e-12)*1e-10 ;
y(1,1:100) = cons./abs(z) ;
plot(z,y,"red") ;

%Plotting graph of the solution obtained through code
hold on ;
box on ;
grid on ;
plot(z,E,"*") ;
xlabel('Distance h') ;
ylabel('Magnitude of E') ;

ERROR

Unable to perform assignment because the left and right sides have a different number of elements in assigning position vectors part.

THIS IS MY CODE PLEASE SUGGEST POSSIBLE CORRECTIONS

[Alan Weiss]

What errors are you getting? What is the specific issue? Please indicate exactly what you need help with.

Alan Weiss

MATLAB mathematical toolbox documentation

[Dyuman Joshi]

Extending Alan's comment - Your syntax is wrong in many places, not sure if that's because you have copy-pasted your code. Correct it and then mention what problems you are facing.

Answer 1

[Walter Roberson]

rz=linspace(-0.5,0.5) ;
rx=zeros(size(rz)) ;
ry=zeros(size(rz)) ;
r=[rx ; ry ; rz] ;
%Assigning variables to the position vectors
syms x [100 1]
size(r)

ans = 1×2

3 100

for i=1 : 100
     x(i)=transpose(r(: , i)) ;
end

Unable to perform assignment because the left and right sides have a different number of elements.

Error in sym/privsubsasgn (line 1229)
L_tilde2 = builtin('subsasgn',L_tilde,struct('type','()','subs',{varargin}),R_tilde);

Error in sym/subsasgn (line 1060)
C = privsubsasgn(L,R,inds{:});

So r is 3 x 100. You loop through by columns, extracting a 3 x 1 vector from it. You transpose that 3 x 1 vector to get a 1 x 3 vector. That is your right hand side. Then you try to assign that 1 x 3 vector to the scalar output location x(i) .

In MATLAB, it is not possible to define a numeric collection with () style indexing such that by using a single subscript, you get the content of the collection. It is possible to do that using {} style indexing.

[Walter Roberson]

%Assigning values of required constants
k=1/(4*pi*8.542e-12) ;
z=linspace(-0.5,0.5) ;
E=zeros(size(z));
Q=1e-10;

%Creating a matrix containing position vectors for the 100 points on the z-axis
rz=linspace(-0.5,0.5) ;
rx=zeros(size(rz)) ;
ry=zeros(size(rz)) ;
r=[rx ; ry ; rz] ;

%Assigning variables to the position vectors
for i=1 : 100
     x{i}=transpose(r(: , i)) ;
end

%Creating a matrix containing position vectors for the 100 points on the y-axis
r1y=linspace(-0.5,0.5) ;
r1z=zeros(size(r1y)) ;
r1x=zeros(size(r1y)) ;
r1=[r1x ; r1y ; r1z] ;

%Assigning variables to the position vectors
for i=1 : 100
    x1{i}=transpose(r1(: , i)) ;
end

%Calculating distance between the points on z-axis and y-axis
for m=1 : 100
     xi(m)=norm(x{m} - x1{m}) ;
end
E=zeros(size(z)) ;
for m=1:100
       E(m)=k*Q / abs(xi(m)) ^ 2 ;
end

%Analytical calculation and plotting graph of the solution
cons=1/(2*pi*8.542e-12)*1e-10 ;
y(1,1:100) = cons./abs(z) ;
plot(z,y,"red") ;

%Plotting graph of the solution obtained through code
hold on ;
box on ;
grid on ;
plot(z,E,"*") ;
xlabel('Distance h') ;
ylabel('Magnitude of E') ;

[Academician]

Oh, so that's the error. I understood now. Thanks for your explaination.