MATLAB: How to use transpose in the graph

transpose

My y-axis is in opposite direction, from 6000 to 0 insted of 0 to 6000.

imagesc(x,y,C) % this is my plot

I have tried

a) imagesc(x,y.',C) % but it did not work.

b) imagesc(x,y',C) % but it did not work.

c) imagesc(x,(flipud(y)),C) % but it did not work.

d) imagesc(x,(fliplr(y)),C) % but it did not work.

Please i need help. Thanks

Best Answer

Put this after imagesc command

set(gca,'Ydir','normal')

imagesc(x,y,flipud(C) )

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MATLAB: Axis control in Image plot

x = [1 5];
y = [1 5];
C = [0 2 4 6; 8 10 12 14; 16 18 20 22];
figure
h1 = axes ;
imagesc(x,y,C) ;
set(h1,'YDir','normal');

MATLAB: How to draw a Lab* colour space or HSV colour space (2D)

As commented in your question, note that you're only plotting one slice of the 3D colour space.

Of course, your original code doesn't work, you end up doing

pcolor(x, y, thg);

so you're only plotting the hue (angle) against x and y. There's no saturation or value information in your plot. You then apply a colour map called hsv whose colours are derived from the hsv cylinder, but in no way does it mean you've done any conversion to/from hsv. The whole idea is flawed.

Here is how I'd do it:

%inputs:
%plotradius: the plot radius of the disk. Image will be 2*plotradius+1 x 2*plotradius+1
%plotvalue:  the Value at which the slice of the HSV cylinder is to be taken. In the range 0-1
plotradius = 100;
plotvalue = 1;
[x, y] = meshgrid(-plotradius:plotradius);  %get x,y coordinates of pixels in image
[hue, saturation] = cart2pol(x, y);  %convert to angle, radius. Angle is the hue, radius is the saturation in the HSV cylinder
hue = (hue + pi) / (2*pi); %rescale from -pi:pi to 0:1 since matlab use 0:1 for the range of the hue
saturation = saturation / plotradius;  %rescale saturation to range 0:1. Not that anything above 1 is outside the cylinder
value = ones(size(hue)) * plotvalue;  %set value constant for all points in the disk
%now set points outside the disk (saturation >1) to white. That'd be a value of 1 and saturation of 0. hue doesn't matter
outsidedisk = saturation > 1;
saturation(outsidedisk) = 0;
value(outsidedisk) = 1;
%finally, convert hsv to rgb and plot
rgb = hsv2rgb(cat(3, hue, saturation, value));
imshow(rgb);

Best Answer

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MATLAB: Axis control in Image plot

MATLAB: How to draw a L*a*b* colour space or HSV colour space (2D)

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MATLAB: How to draw a Lab* colour space or HSV colour space (2D)