Can someone help me with this error message: Error using vertcat Dimensions of arrays being concatenated are not consistent. ? My code is attached below

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eul.m (source code)
function [t,y] = eul(fun,a,b,y0,N)
%Euler's method for solving the IVP
% y' = f(t,y) in [a,b], y(a) = y0
h = (b-a)/N;
t = zeros(N+1,1);
y = zeros(N+1,1);
t(1) = a;
y(1) = y0;
for i = 1:N
t(i+1) = t(i) + h;
y(i+1) = y(i) + h*fun(t(i),y(i));
end
----------------------------
exercise1 (driver file)
y0 = -2; % initial condition
a = 0; % starting time
b = 2; % ending time
N1 = 5; % number of subintervals, h = (b-a)/N
[t1,y1] = eul(fun,a,b,y0,N1);
N2 = 10;
[t2,y2] = eul(fun,a,b,y0,N2);
N3 = 20;
[t3,y3] = eul(fun,a,b,y0,N3);
%% Display Solution
exactY = @(t) -1./t;
Y = exactY(t);
disp('----------------------------------------------------');
disp('t_i True Euler 5 Euler 10 Euler 20')
disp('----------------------------------------------------')
formatSpec = '%.1f % .5f % .5f % .5f % .5f\n';
fprintf(formatSpec,[t1';Y';y1';y2(1:2:N2+1)'; y3(1:4:N3+1)']) // I think the problem is with this line but I don't know where.
The driver file runs when N1 =10, N2 = 20, and N3 = 40, but not the values I need. Any help is appreciated!

Answers (1)

Cris LaPierre
Cris LaPierre on 19 Feb 2021
Edited: Cris LaPierre on 19 Feb 2021
This error occurs when you try to combine (stack) vectors with different number of columns.
a=1:3;
b=2:8;
c=[a;b]
Error using vertcat
Dimensions of arrays being concatenated are not consistent.
Check that you have the same number of elements in each item you are trying to combine/stack.
[t1';Y';y1';y2(1:2:N2+1)'; y3(1:4:N3+1)']
Perhaps you meant to use commas instead of semicolons?
d=[a,b]
d = 1×10
1 2 3 2 3 4 5 6 7 8

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