Question

Is there a way to turn the y axis upside down in matlab plots, so that the positive direction of the y axis, instead of up, points down ?

(I beg of you; please do not say, print it out, then turn the paper around 😉

Answer 1

The 'YDir' axes property can be either 'normal' or 'reverse'. By default it is 'normal' for most plots, but some plots will automatically change it to 'reverse', such as the image or imagesc functions.

You can set the y-axis direction of an axes with either the set function or dot indexing (in newer MATLAB versions):

h = gca;  % Handle to currently active axes
set(h, 'YDir', 'reverse');
% or...
h.YDir = 'reverse';

I’m baffled by some of the other answers saying that the 'YDir' property has somehow disappeared or is giving an error. I haven’t seen any such behavior in versions of MATLAB from 2013, 2014, or 2016. There are only two potential pitfalls I came across:

• The property can’t be set with a cell array, only a character string:

  >> set(gca, 'YDir', {'reverse'});
  Error using matlab.graphics.axis.Axes/set
  While setting property 'YDir' of class 'Axes':
  Invalid enum value. Use one of these values: 'normal' | 'reverse'.
  

  although this works:

  set(gca, {'YDir'}, {'reverse'});  % Property name is also a cell array
  

• The gca function can’t be used interchangeably as a handle when performing dot indexing (which is why I first saved it to a variable h in the above example):

  >> gca.YDir
  Undefined variable "gca" or class "gca.YDir". 
  >> gca.YDir = 'reverse'  % Creates a variable that shadows the gca function
  gca = 
    struct with fields:
  
      YDir: 'reverse'
  

Finally, if you want some code that will toggle the 'YDir' property no matter what its current state is, you can do this:

set(gca, 'YDir', char(setdiff({'normal', 'reverse'}, get(gca, 'YDir'))));
% or...
h = gca;
h.YDir = char(setdiff({'normal', 'reverse'}, h.YDir));