Error plotting (Vector must be the same length)

1 次查看(过去 30 天)
clear all
clc
f=@(t,y) 4*y.^2;
F = @(t) 1/(4*(1-t));
a=0; b=0.95;
h=0.05;
n = (b-a)/h;
t = a:h:b;
y = zeros(1,length(t));
y(1) = 0.25;
%EULERS METHOD
for i = 2:n+1
y(i) = y(i-1) + h*f(t(i-1),y(i-1));
end
E=y;
fprintf(' Step number_i time_t Approximated solution Exact solution Relative Error\n')
for j = 1:n+1
m=abs(E(j)-F(t(j)));
n = abs(F(t(j)));
kE = m/n;
A(j) = F(t(j));
fprintf('%5d %18f %15f %20f %15f \n',j,t(j),E(j),F(t(j)),kE)
end
plot(t,A,'.-k', t, E, 'o-r')
xlabel('x');
ylabel('y(t)');
grid on
title('Part(a) Plot');
legend('Exact solution','Eulers solution')
**It all works for the table, but I'm getting an error for plotting. It says the vectors should be in the same length, but I don't get the problem.
Please help me.
Thank you.

回答(1 个)

Davide Masiello
Davide Masiello 2022-4-13
编辑:Davide Masiello 2022-4-14
The vector A has 19 elements, whereas t and E have 20.
clear all
clc
f=@(t,y) 4*y.^2;
F = @(t) 1/(4*(1-t));
a=0; b=0.95;
h=0.05;
n = (b-a)/h;
t = a:h:b;
y = zeros(1,length(t));
y(1) = 0.25;
%EULERS METHOD
for i = 2:n+1
y(i) = y(i-1) + h*f(t(i-1),y(i-1));
end
E=y;
fprintf(' Step number_i time_t Approximated solution Exact solution Relative Error\n')
Step number_i time_t Approximated solution Exact solution Relative Error
for j = 1:n+1
m=abs(E(j)-F(t(j)));
n = abs(F(t(j)));
kE = m/n;
A(j) = F(t(j));
fprintf('%5d %18f %15f %20f %15f \n',j,t(j),E(j),F(t(j)),kE)
end
1 0.000000 0.250000 0.250000 0.000000 2 0.050000 0.262500 0.263158 0.002500 3 0.100000 0.276281 0.277778 0.005387 4 0.150000 0.291548 0.294118 0.008738 5 0.200000 0.308548 0.312500 0.012648 6 0.250000 0.327588 0.333333 0.017237 7 0.300000 0.349051 0.357143 0.022658 8 0.350000 0.373418 0.384615 0.029114 9 0.400000 0.401306 0.416667 0.036866 10 0.450000 0.433515 0.454545 0.046266 11 0.500000 0.471102 0.500000 0.057795 12 0.550000 0.515490 0.555556 0.072118 13 0.600000 0.568636 0.625000 0.090183 14 0.650000 0.633305 0.714286 0.113373 15 0.700000 0.713520 0.833333 0.143776 16 0.750000 0.815343 1.000000 0.184657 17 0.800000 0.948299 1.250000 0.241361 18 0.850000 1.128154 1.666667 0.323108 19 0.900000 1.382700 2.500000 0.446920
plot(t(1:end-1),A,'.-k', t(1:end-1), E(1:end-1), 'o-r')
xlabel('x');
ylabel('y(t)');
grid on
title('Part(a) Plot');
legend('Exact solution','Eulers solution')
  2 个评论
Seungryul Lee
Seungryul Lee 2022-4-13
do you know how to use only first 19 elements of t and E, so that I can plot it?
How can I get rid of the last element of t and E
Davide Masiello
Davide Masiello 2022-4-13
编辑:Davide Masiello 2022-4-14
Yes
plot(t(1:end-1),A,'.-k', t(1:end-1), E(1:end-1), 'o-r')
I updated it in the answer too, so you can see the resulting plot.

请先登录,再进行评论。

类别

Help CenterFile Exchange 中查找有关 2-D and 3-D Plots 的更多信息

标签

产品


版本

R2022a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by