How can I incorporate both the x-axis and a reversed y-axis without altering the plot but only adjusting the orientation of the axes?

Hello everyone,

I hope you're all doing well. I attempted to run the provided code and noticed that associating an x and y axis, or an x-axis with a -y axis, results in the matrix plot being flipped, causing the y-axis to display in descending order. My goal is to keep the matrix unchanged and only flip the labeling of the y-axis based on the provided y values.

Thank you in advance for your assistance.

Best regards.

Code:

clear all

clc

a=[0 0 1; 1 1 0; 1 0 1];

x=linspace(-1,1,3);

y=linspace(-2,2,3);

subplot 121

imagesc(x,y,a)

subplot 122

imagesc(x,-y,a)

Answer 1

[Hassaan]

@Rabih Sokhen Try this.

clear all;
clc;
a = [0 0 1; 1 1 0; 1 0 1];
x = linspace(-1, 1, 3);
y = linspace(2, -2, 3);  % Define y from positive to negative

% First subplot with y-axis from 2 to -2
subplot(121);
imagesc(x, y, a);  % Plot the data
set(gca, 'YDir', 'normal'); % Make sure the y-axis starts from the bottom
title('Y Axis from 2 to -2');
xlabel('x');
ylabel('y');

% Second subplot with y-axis labels reversed
subplot(122);
imagesc(x, y, a);  % Plot the data
set(gca, 'YDir', 'normal'); % Keep the y-axis direction normal

% Get the current y-tick locations
yticks = get(gca, 'YTick');

% Map the y-tick locations to the reversed y-values
% The new y-tick labels should match the reversed y values but the data should stay the same
new_yticklabels = linspace(max(y), min(y), numel(yticks));

% Set the y-tick labels to the reversed y-values
set(gca, 'YTickLabel', new_yticklabels);

title('Y Axis Reversed');
xlabel('x');
ylabel('y');

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[Rabih Sokhen]

Thank you for your response. Your code served as inspiration, and I have created the following code based on it:

code:

clear all

clc

a = [0 0 1; 1 1 0; 1 0 1];

x = linspace(-1, 1, 3);

y = linspace(1, 5, 3);

subplot 121

img2(x,y,a)

subplot 122

img2(-x, -y, a)

function img2(varargin)

if numel(varargin) == 1

a = varargin{1};

a=squeeze(a); % squeeze will ilimate the dimention of size 1 to do the plot

[xx ,yy] = size(a);

x = linspace(1,yy,yy);

y = linspace(1,xx,xx);

elseif numel(varargin) == 3

[x ,y, a] = deal(varargin{1:3});

else

error('IMG: incorrect number of arguments')

end

[xx , yy] = size(a);

if (xx==numel(y) && yy==numel(x)) % this condition is not necessary

dx = (x(end)-x(1))/(yy-1);

dy = (y(end)-y(1))/(xx-1);

xg = linspace(x(1)-dx/2,x(end)+dx/2,yy+1);

yg = linspace(y(1)-dy/2,y(end)+dy/2,xx+1);

if y(2)>y(1) && x(2)>x(1)

imagesc(x,y,a);

set(gca,'YDir','normal');

end

if y(2)<y(1)

a=flipud(a);

end

if(x(2)<x(1))

a=fliplr(a);

end

if(x(2)<x(1) || y(2)<y(1))

imagesc(x,y,a);

set(gca,'YDir','normal');

end

if y(2)<y(1)

set(gca, 'YDir', 'reverse'); % This flips the y-axis direction

end

if x(2)<x(1)

set(gca, 'XDir', 'reverse'); % This flips the y-axis direction

end

%add pixel info with position

hp=impixelinfo;

% set(hp,"Position",[1720 1 200 20]);

hold on;

%option

hm = mesh(xg,yg,zeros([xx yy]+1));

hm.FaceColor = 'none';

hm.EdgeColor = 'k';

hm.EdgeAlpha = 0.5;

hold off

else

error('IMG: Length of X and Y must match the size of A')

end

end

[Rabih Sokhen]

Answer 2

[Amish]

Hi Rabih,

I understand that you want the matrix to reamin the same while the y-axis is flipped. In order to flip the labeling of the y-axis while keeping the matrix plot unchanged, you can use the "set(gca, 'YDir', 'normal')" or "set(gca, 'YDir', 'reverse')" command after plotting your data with "imagesc" function. This command changes the direction of the y-axis without altering the data in the matrix.

Here is the modified code to do the same:

clear all
clc
a = [0 0 1; 1 1 0; 1 0 1];
x = linspace(-1, 1, 3);
y = linspace(-2, 2, 3);

% Plot with normal y-axis
subplot(121)
imagesc(x, y, a);
set(gca, 'YDir', 'normal'); % This keeps the y-axis direction as is
title('Normal Y-Axis');

% Plot with flipped y-axis labels
subplot(122)
imagesc(x, y, a); % Keep the matrix 'a' the same
set(gca, 'YDir', 'reverse'); % This flips the y-axis direction
title('Flipped Y-Axis');

Here are some documentation links for your reference:

imagesc : https://www.mathworks.com/help/matlab/ref/imagesc.html

gca : https://www.mathworks.com/help/matlab/ref/gca.html

set :https://www.mathworks.com/help/matlab/ref/set.html

Hope this helps!