How to flip a line upside down?

How can I flip this line upside down:

This is my code that may not need flipud() :

x = [1 2 3];
y = [2 2.5 3.5];
flipud(plot(x,y))

[Adam]

The result of the plot instruction is a handle to the graphics object which is a scalar 'Line' object. Flipping this will do nothing at all!

[Ezz El-din Abdullah]

Why is the 'line' a scalar object not an array?

[Adam]

Because it is a line object. There is only one line. Of course, it depends what version of Matlab you are using. If you are < R2014b then it will simply be a 'magic' double which you can query for the line properties.

Take a look at the output of

h = plot( x, y )

on the command line and you will see what it is. It is an object containing many useful properties of the line - e.g. colour, width, x data, y data

Answer 1

[Adam]

figure; hAxes = gca;

x = [1 2 3];
y = [2 2.5 3.5];
plot( hAxes, x, y )

set( hAxes, 'YDir', 'reverse' ) % Or hAxes.YDir = 'reverse' from R2014b onwards

[Ezz El-din Abdullah]

Thanks!

This works fine for the above code, but when I applied it on the other code it doesn't work.

This one:

hAxes = gca;
% pixLoc(): a function that gets the locations 
% of the desired pixels i.e. returns their columns and rows
[cp,rp] = pixLoc(Ic,6,4,38,348); 
% a black image with the same size of the image Ic
imshow(imrotate(0*Ic,90)) 
hold on
% plotting points that I would like to flip 
% (the blue points in the figure below)
plot(hAxes,cp,rp,'o');
hAxes.YDir = 'reverse';

[Adam]

What do you actually mean by flipping? What result do you expect from this? Do you want the max y value and min y value to be exchanged so that the curve is upside down? In that case you need to manipulate the data rather than the plot as e.g.

data = max( data ) - data + min( data );

[Ezz El-din Abdullah]

I mean it's like considering the image a paper and I would like to flip it over upside down so that e.g. the point at y=20 will be at y=70 and so on.

Is it clear now?

[Adam]

Then you probably want the above maths or something similar. If you want 20 to become 70 then just substitute 70 and 20 in instead of max( data ) and min( data )