How can I invert the position of a vector?

In the following code I'm trying to invert the position of vector "y"; I'm expecting to pass from something like this y=[a b c d] to y=[d c b a], and I don't know how can I plot the result for this two vectors.

The code is shown next

%close everything and clear everything
close all;
clear all;
clc;

% First we read an image wich must contain a graphic in it and then convert it to black and white
A=im2bw(imread('prueba3.png'));
%Show the image
figure();
imshow(A);
%Obtain the rows and columns
[F,U]=size(A);

i=1;
%Then we "swap" the matrix looking for the black pixels defined by a 0 and save the
%position "(F,U)" in the vector "x" and "y"
for n=1:U;
     for m=1:F;
         if A(m,n)~=1;
             x(i)=n;
             y(i)=m;

           else
               m=m+1;
           end
       end
       n=n+1;  
       i=i+1;
  end
  %How can I invert the positions of the "y" vector and then plot(x,y) even
  %though it changed the dimension of y vector?

figure();
plot(x,y);

The Image I've been using is this

The resultant graphic I'm getting is shown as figure 2:

In wich we can see that the vector "y" is inverted

I'm also looking for the 0 generated in y(0,0)

Thank you so much for your help!

Answer 1

[Walter Roberson]

Easiest way:

set(gca, 'YDir', 'reverse')

[Raul Torres]

Thank you so much man. it worked :)