Please fix my code

to solve y'=t(y.^2-4)

I try like this.

but something was wrong... Amend pls......

clear all
[x,y]=meshgrid(linspace(0,3,100));
u=ones(100);
v=(y.^2-4)*(1/2).*(log(abs(2-y/2+y)).^(1/2));
quiver(x,y,u,v,0.8)
hold on
 
t=0, w=1;
dt=0.01;
N=1/dt;
 
for n=1:N
    t=t+dt;
    w=w+dt*(y.^2-4)*(1/2).*(log(abs(2-y/2+y)).^(1/2));
    st=[st t
end
plot(st,sw,'r')

what is wrong?

[Dyuman Joshi]

Where does your error occur? What is y?

There's a syntax error in the last line of the for loop.

[DGM]

This line is simply incomplete.

st=[st t

if you want to do

st=[st t];

Then st needs to exist first (maybe as just st = [];)

and you're trying to plot sw, which doesn't exist at all. I'm not inclined to guess at the value or meaning of a missing variable.

[지원 안]

clear all

[x,y]=meshgrid(linspace(0,3,100));

u=ones(100);

v=(y.^2-4)*(1/2).*(log(abs(2-y/2+y)).^(1/2));

quiver(x,y,u,v,0.8)

hold on

t=0, w=1;

dt=0.01;

N=1/dt;

st=t; sw=w;

for n=1:N

t=t+dt;

w=w+dt*(y.^2-4)*(1/2).*(log(abs(2-y/2+y)).^(1/2));

st=[st t]; sw=[sw w];

end

plot(st,sw,'r')

but something wrong... what's wrong?

[DGM]

What's the error message say?

Error using horzcat
Dimensions of arrays being concatenated are not consistent.
    sw=[sw w];

so look at the size of sw and w

>> size(sw)
ans =
     1     1
>> size(w)
ans =
   100   100

why is sw the size it is? It's initialized as 1. You could initialize it as an empty vector [], but pay attention to the size of w.

w=1;
% ...
sw=w;

why is w the size it is?

[x,y]=meshgrid(linspace(0,3,100));
% ...
w=w+dt*(y.^2-4)*(1/2).*(log(abs(2-y/2+y)).^(1/2));

w is 2D. You're going to figure out how you want to plot these. Once you figure that out, you'll have to figure out how you need to store them. If you need to store all instances of them, you can concatenate them on dim3.