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

clear all; 
close all;
clc;

%% Define Parameters
Yo = 250; %Yield stress (N/mm^2)
Do = 15; %Diameter of the die inlet (mm)
D1 = 9; %Diameter of the die outlet (mm)
Eps = 300; %Strain hardening exponent
u = 0; % Friction coefficient 

%% Initialize Variables
x(1)=0;
SigmaX(1)=0; 
D=Do;
Y=Yo;
p(1)=Yo; %Die pressure
alpha = 12*(pi/180); %radians

%% Define number of slices
n = 100;

%% Calculate step size 
dD = (Do-D1)/n;
dx = dD/(2*tan(alpha));

%% Begin loop
for i = 2:n+1
    dSigmaX=(2/D)*(SigmaX+((Y-SigmaX)*(1+u*cot(alpha))))*dD;
    SigmaX(i)=SigmaX(i-1)+dSigmaX; 
    D = D-dD;
    Epsilon = 2*log(Do/D);
    Y = Yo+(Eps*Epsilon);
    p(i) = Y-SigmaX(i);
    x(i) = x(i-1)+dx;
end

%% Plots 
plot(x, SigmaX, 'o', x, p, '*')
xlabel('x')
ylabel('Pressure')
title('Case A')
grid on 

**SigmaX(i)=SigmaX(i-1)+dSigmaX; ** this line is giving me the error 'Unable to perform assignment because the left and right sides have a different number of elements.'

[Jacob Wood]

It looks like dSigmaX is a vector, instead of a single element, if SigmaX is a vector. Perhaps you want something like:

dSigmaX=(2/D)*(SigmaX(i-1)+((Y-SigmaX(i-1))*(1+u*cot(alpha))))*dD;

Answer 1

[Srivardhan Gadila]

From line 24, the size of dSgimaX is same as the size of SigmaX which is increasing after every iteration.

In line 25 "SigmaX(i-1)+dSigmaX" is a vector and we are assigning it to a scalar (i.e., an element of the array SigmaX), which is the cause of the error.