Changing orientation of color map

How can I change the orientation of color difference from horizontal to vertical. Now it becomes "cooler" from 0 to x. as shown in first screenshot, but I want it to become cooler in y direction as in second screenshot

x = linspace(0,3*pi,200);
y = (cos(x) + rand(1,200))*(-1);
size=(10*x+0.01);
colormap cool
c = linspace(1,-10,length(x));
scatter(x,y,size,c, 'filled')

<-- My result <-- Preferred Result

Answer 1

[Image Analyst]

Try using the scaled y values as the index into your colormap:

x = linspace(0,3*pi,200);
y = (cos(x) + rand(1,200))*(-1);
sizes = (10*x+0.01);
cmap = cool(256);
% Get the row of cmap that corresponds to the y value.
rows = round(rescale(y, 1, size(cmap, 1)));
colors = cmap(rows, :);
scatter(x, y, sizes , colors, 'filled')
grid on;

To reverse the colors, use fllipud() on the colormap.

x = linspace(0,3*pi,200);
y = (cos(x) + rand(1,200))*(-1);
sizes = (10*x+0.01);
cmap = flipud(cool(256));
% Get the row of cmap that corresponds to the y value.
rows = round(rescale(y, 1, size(cmap, 1)));
colors = cmap(rows, :);
scatter(x, y, sizes , colors, 'filled')
grid on;

Answer 2

[Oguzhan Alkan]

The orientation of color difference is changed from horizontal to vertical.

Does anyone know how to do this? This is what should be done in the assignment

[Image Analyst]

Not sure what you mean. The colors of the markers DO change as you move vertically.

If you want the colors to change horizontally, just change y to x:

x = linspace(0,3*pi,200);
y = (cos(x) + rand(1,200))*(-1);
sizes = (10*x+0.01);
cmap = cool(256);
% Get the row of cmap that corresponds to the x value.
rows = round(rescale(x, 1, size(cmap, 1)));
colors = cmap(rows, :);
scatter(x, y, sizes , colors, 'filled')
grid on;

Again, explain exactly what you mean because you seem to be asking for exactly what my accepted answer already does. What do you want different????