Set or query axes alpha limits
alpha_limits = alim
alim_mode = alim('mode')
alpha_limits = alim returns the alpha limits (ALim property) of the current axes.
alim([amin amax]) sets the alpha limits to the specified values. amin is the value of the data mapped to the first alpha value in the alphamap, and amax is the value of the data mapped to the last alpha value in the alphamap. Data values in between are linearly interpolated across the alphamap, while data values outside are clamped to either the first or last alphamap value, whichever is closest.
alim_mode = alim('mode') returns the alpha limits mode (ALimMode property) of the current axes.
auto — MATLAB® automatically sets the alpha limits based on the alpha data of the objects in the axes.
manual — MATLAB does not change the alpha limits.
Map transparency to a surface plot of z-data and change the alim property to make all values below zero transparent:
[x,y] = meshgrid([-2:.2:2]); z = x.*exp(-x.^2-y.^2); % Plot the data, using the gradient of z as % the alphamap: surf(x,y,z+.001,'FaceAlpha','flat',... 'AlphaDataMapping','scaled',... 'AlphaData',gradient(z),... 'FaceColor','blue'); axis tight % Adjust the alim property to see only where % the gradient is between 0 and 0.15: alim([0 .15])