Unable to perform assignment because the size of the left side is 1-by-1 and the size of the right side is 1-by-2.

I get the error "Unable to perform assignment because the size of the left side is 1-by-1 and the size of the right side is 1-by-2." when I run the script. I am not sure where I am going wrong.

function script:

function [w1i, w2i, ti] = Basic_Euler(h ,m1 ,m2 , k1, k2, k3, c1, c2, c3, z1, z2,N,t0, x1,x2, tf)

neqn1 = length (x1);

neqn2 = length (x2);

ti = linspace ( t0, tf, N+1 );

w1i = [zeros( neqn1, N+1 ) ];

w2i = [zeros( neqn2, N+1 ) ];

for i = 1:N

z1(i+1) = z1(i) + h.*(((c2.*z2(i))-((c1+c2).*z1(i))+(k2.*x2(i))-((x1(i).*(k1+k2))))./m1);

x1(i+1) = x1(i) + h.*(z1(i));

z2(i+1) = z2(i) + h.*(((c2.*z1(i))-((c2+c3).*z2(i))+(k2.*x1(i))-((k2+k3).*x2(i)))./m2);

x2(i+1) = x2(i) +h.*(z2(i));

w1i(1:neqn1,i+1) = x1;

w2i(1:neqn2,i+1) = x2;

end

end

Master Script:

function Ass2()

close all

t0 = 0;

tf = 100;

h = 0.1;

N = (tf - t0)./h;

k1 = 3;

k2 = 2;

k3 = 1;

c3 = 0.01;

m2 = 4;

c1 = 0.03;

c2 = 0.02;

m1 = 1;

x1 = -1;

x2 = 6;

z1 = -1;

z2 = 3;

[x1,x2, ti] = Basic_Euler(h ,m1 ,m2 , k1, k2, k3, c1, c2, c3, z1, z2,N,t0, x1,x2, tf);

figure1 = figure;

axes1 = axes('Parent',figure1,'FontSize',20,'FontName','Times New Roman');

box(axes1,'on');

grid(axes1,'on');

hold(axes1,'all');

xlabel('t','FontSize',20,'FontName','Times New Roman');

ylabel('x','FontSize',20,'FontName','Times New Roman');

plot1 = plot(ti,x1,'Parent',axes1,'LineWidth',3);

set(plot1(1),'Marker','diamond','DisplayName','Basic Euler 1');

legend(axes1,'show');

figure2 = figure;

axes1 = axes('Parent',figure2,'FontSize',20,'FontName','Times New Roman');

box(axes1,'on');

grid(axes1,'on');

hold(axes1,'all');

xlabel('t','FontSize',20,'FontName','Times New Roman');

ylabel('x','FontSize',20,'FontName','Times New Roman');

plot1 = plot(ti,x2,'Parent',axes1,'LineWidth',3);

set(plot1(1),'Marker','diamond','DisplayName','Basic Euler 1');

legend(axes1,'show')

Answer 1

[Pavan Guntha]

Hi Shaan,

The error is due to the line 15 of the function Basic_Euler:

w1i(1:neqn1,i+1) = x1;

The size of x1 is getting changed within the function due to the line:

x1(i+1) = x1(i) + h.*(z1(i));

Because of this reason, the size mismatch is happening. The possible solution might be to change the line 15 & 16 in the function as follows:

w1i(1:neqn1,i+1) = x1(i+1);
w2i(1:neqn2,i+1) = x2(i+1);

Hope this helps!

[Shaan Singh]

Thank you very much Mr Guntha! It was very helpful and solved the error I was having.

[darova]