Usage Of "goto" for previous lines

hello guys Iva had a simple but confusing question... i was writing a program for Euler's formula, then I found out Matlab doesn't have any "goto" function for refering to previous lines . i was looking for an alternate and i will appreciate it if you guys help me with this :) here's an example:

      x=[0.1:0.1:1]
      h=0.1
      i=1
      y(1)=1
      Z(1)=1.1
      Y(1)=1.1
      %Y'=y*(x^(1/3))
      while i<11
        y(i+1)=y(i)+(h*(x(i)*(y(i)^(1/3))))
        Z(i+1)=(x(i+1)*(y(i+1)^(1/3)))
line**  y(i+1)=y(i)+(0.5*h*(Y(i)+Z(i+1)))
        Y(i+1)=x(i+1)+y(i+1)
        if abs(Y(i+1)-Z(i+1))>0.00000000001
          Z(i+1)=Y(i+1)
          goto(line**)
        end
i=i+1
end

[Stephen23]

A search using the "Search" field at the top of this page and the term "goto" produces 211 results. Have you checked any of them?

[Stephen23]

You should not use i for your loop variable, as this is the name of the inbuilt imaginary unit .

Answer 1

[Azzi Abdelmalek]

Insert this code

test=1;
while test==1
      y(i+1)=y(i)+(0.5*h*(Y(i)+Z(i+1)))
      Y(i+1)=x(i+1)+y(i+1)
      if abs(Y(i+1)-Z(i+1))>0.00000000001
          Z(i+1)=Y(i+1)
          test=1;
      else
          test=0;
      end
end

[Hossein]

thnx a lot azzi :)

Answer 2

[Stephen23]

Try this:

x = 0.1:0.1:1;
h = 0.1;
y(1) = 1;
Z(1) = 1.1;
Y(1) = 1.1;
%Y'=y*(x^(1/3))
for k = 1:9
    y(k+1) = y(k)+(h*(x(k)*(y(k)^(1/3))));
    Z(k+1) = (x(k+1)*(y(k+1)^(1/3)));
    while true
        y(k+1) = y(k)+(0.5*h*(Y(k)+Z(k+1)));
        Y(k+1) = x(k+1)+y(k+1);
        if abs(Y(k+1)-Z(k+1))<=0.00000000001, break, end
        Z(k+1) = Y(k+1);
    end
end

Note that this kind of code style can easily end up in an infinite loop, so you might want to consider how to prevent this. And to be honest this looks like a good contender for some serious rewriting as proper MATLAB code, i.e. fully vectorized .