# Error in multiplication of arrays

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Athira T Das on 8 Jul 2022
Answered: KSSV on 8 Jul 2022
clc; clear all; close all;
syms m1 m2 s1 s2 j1 j2
I = 0;
lambda = 1060*10^-9;
M=2
M = 2
z=linspace(0.0001,10000);
wo = 0.02;
C = 10^(-7);
k=2*pi/lambda;
po=(0.545*C^2*k^2*z).^(-(3/5));
b=0.1;
T1=0;
T2=0;
T3=0;
T4=0;
T5=0;
T6=0;
delta= ((1i*k)./(2*z))+(1./(wo.^2))+(1./(po.^2));
delta_star= subs(delta, 1i, -1i);
etta = delta_star - (1./(delta.*po.^4));
X=((k./(2.*z)).^2).*((1./(2.*1i.*sqrt(delta))).^M).*(1./(16.*delta.*etta));
alpha = (1i.*k./(2.*z)).*(1./(delta.*po.^2)-1);
beta_p = (b./(2.*wo)).*(1./(delta.*po.^2)+1);
beta_n = (b./(2.*wo)).*(1./(delta.*po.^2)-1);
A = (alpha.^2./etta)-((k.^2)-(4.*z.^2.*delta));
B1_p = ((1i.*k.*b)./(2.*z.*wo.*delta))+((2.*alpha.*beta_p)./etta);
B1_n = ((1i.*k.*b)./(2.*z.*wo.*delta))+((2.*alpha.*beta_n)./etta);
B2_p = -(((1i.*k.*b)./(2.*z.*wo.*delta))+((2.*alpha.*beta_p)./etta));
B2_n = -(((1i.*k.*b)./(2.*z.*wo.*delta))+((2.*alpha.*beta_n)./etta));
C1_p = ((b.^2)./(4.*wo.^2.*delta))+(((beta_p).^2)./etta);
C1_n = ((b.^2)./(4.*wo.^2.*delta))+(((beta_n).^2)./etta);
C2_p = ((b.^2)./(4.*wo.^2.*delta))+(((beta_n).^2)./etta);
C2_n = ((b.^2)./(4.*wo.^2.*delta))+(((beta_p).^2)./etta);
for m1 =0:M
T2=0;
for m2=0:M
T3=0;
for s1=0:m1/2
T4=0;
for j1=0:m1-2*s1
T5=0;
for s2=0:(M-m1)/2
T6=0;
for j2=0:(M-m1-(2*s2))
e1=(exp(C1_n).*hermiteH(m2+j2,((1i.*beta_n)./sqrt(etta))))+(exp(C2_p).*hermiteH(m2+j2,((-1i.*beta_p)./sqrt(etta))));
e2=(exp(C1_p).*hermiteH(m2+j2,((1i.*beta_p)./sqrt(etta))))+(exp(C2_n).*hermiteH(m2+j2,((-1i.*beta_n)./sqrt(etta))));
e3=(exp(C1_p).*hermiteH(M-m2+j2,((1i.*beta_p)./sqrt(etta))))+(exp(C2_n).*hermiteH(M-m2+j2,((-1i.*beta_n)./sqrt(etta))));
e4=(exp(C1_n).*hermiteH(M-m2+j2,((1i.*beta_n)./sqrt(etta))))+(exp(C2_p).*hermiteH(M-m2+j2,((-1i.*beta_p)./sqrt(etta))));
T6=T6+nchoosek(M-m1-(2.*s2),j2).*((1./(2.*1i.*sqrt(etta))).^(M-m2+j2)).*((1./(po.^2)).^j2).*((b./2.*wo).^(M-m1-2*s2-j2)).*e1.*e2.*e3.*e4;
end
T5=T5+T6.*(((factorial(M-m1).*(-1).^s2)./(factorial(s2).*factorial(M-m1-2.*s2))).*(((2.*1i)./(delta.^(0.5))).^(M-m1-2.*s2)));
end
T4=T4+T5.*nchoosek(m1-(2.*s2),j1).*((1./(2.*1i.*sqrt(etta))).^(m2+j2)).*((1./(po.^2)).^j1).*((b./2.*wo).^(m1-2.*s1-j1));
end
T3=T3+T4.*(((factorial(m1).*(-1).^s1)./(factorial(s1).*factorial(m1-2.*s1))).*(((2.*1i)./(delta.^(0.5))).^(m1-2.*s1)));
end
T2=T2+T3*nchoosek(M,m2)*((-1i)^(M-m2));
end
T1=T1+T2*nchoosek(M,m1)*((1i)^(M-m1));
end
Error using .*
Array sizes must match.
I0 = -real(X.*T1);
% convert to numerical double
I_numerical = double(vpa(I0))

KSSV on 8 Jul 2022
Check this:
nchoosek(m1-(2.*s2),j1)
this is giving you an expty matrix.
A = rand(1,5) ;
B = zeros([],1)
B = 0×1 empty double column vector
A*B
Error using *
Incorrect dimensions for matrix multiplication. Check that the number of columns in the first matrix matches the number of rows in the second matrix. To operate on each element of the matrix
individually, use TIMES (.*) for elementwise multiplication.
Use nchoosek use wisely.

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