# Change the background colour gradient.

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RAJEEV on 25 Jun 2024
Commented: RAJEEV on 1 Jul 2024
Is there any way of changing the background colour of a MATLAB plot. I want to apply changes in the CTF Plot11.fig file and the idea I acquired was from a picture on wikipedia page "2013_Atmospheric_absorption_of_electromagnetic_waves".
https://en.wikipedia.org/wiki/Electromagnetic_spectrum

Adam Danz on 25 Jun 2024
Edited: Adam Danz on 26 Jun 2024
The axes color property can only be set to one solid color.
A workaround is to plot a patch with interpolated colors and to set the patch's size to match the axes' limits. By assigning a LimitsChangedFcn, you can automatically update the patch to match the axes limits any time the limits are changed.
% Create axes
fig = figure();
ax = axes(fig);
% Create interpolated patch
% You won't see the patch until the vertices are updated when the
% axes limits change. If you want to update the vertices right away,
% call updateAxesBackground(p) after creating the patch.
px = nan(1,4);
py = nan(1,4);
pc = [1 1 0 0];
p = patch('Faces', 1:4, ...
'Vertices', [px.',py.'], ...
'FaceVertexCData',pc.', ...
'FaceColor','interp', ...
'EdgeColor','none', ...
'Parent',ax);
% Assign a limitsChangeFunction so that when the axes limits are changed,
% the background patch updates its extents (here's the magic sauce)
ax.XAxis.LimitsChangedFcn = @(~,~)updateAxesBackground(p);
% Set colormap - here's where the colors come from
ax.Colormap = sky(256);
hold on
area(ax,reshape(magic(10),[],1),'FaceColor',[.8 .8 .8])
function updateAxesBackground(p)
% update background patch to fill axes
% p is a patch handle.
if isgraphics(p) % skip if p no longer exists
ax = ancestor(p,'axes');
% Escape from recursion by ensuring limits don't change
originalLimits = [ax.XLim, ax.YLim];
returnLimits = onCleanup(@()set(ax,'XLim',originalLimits(1:2),'YLim',originalLimits(3:4)));
% Update vertices
px = ax.XLim([1 2 2 1]);
py = ax.YLim([2 2 1 1]);
p.Vertices = [px.',py.'];
end
end
Adam Danz on 26 Jun 2024
Edited: Adam Danz on 26 Jun 2024
Here's a demo.
In this version the patch is defined by the 6 coordinates shown in the drawing below and the (x,y) coordinates of your line.
This version is more complicated and less efficient than the simpler version in my original answer above.
% line data
y = reshape(magic(10),[],1);
x = 1:100; % Must be monotonically increasing
% Create axes
fig = figure();
ax = axes(fig);
% Create interpolated patch
% You won't see the patch until the vertices are updated when the
% axes limits change. If you want to update the vertices right away,
% call updateAxesBackground(p) after creating the patch.
ny = numel(y);
% px = [max(x,[],'all');min(x,[],'all');x(:)];
px = [x(end); nan(4,1); x(1); x(:)];
py = [nan(6,1); y(:)];
pc = [nan(6,1); y(:)];
p = patch('Faces', 1:ny+6, ...
'Vertices', [px, py], ...
'FaceVertexCData',pc, ...
'FaceColor','interp', ...
'EdgeColor','none', ...
'Parent',ax);
% Assign a limitsChangeFunction so that when the axes limits are changed,
% the background patch updates its extents (here's the magic sauce)
ax.XAxis.LimitsChangedFcn = @(~,~)updateAxesBackground(p);
% Set colormap - here's where the colors come from
ax.Colormap = sky(256);
hold on
plot(ax,x,y,'k-','LineWidth',3)
function updateAxesBackground(p)
% update background patch to fill axes
% p is a patch handle.
if isgraphics(p) % skip if p no longer exists
ax = ancestor(p,'axes');
% Escape from recursion by ensuring limits don't change
originalLimits = [ax.XLim, ax.YLim];
returnLimits = onCleanup(@()set(ax,'XLim',originalLimits(1:2),'YLim',originalLimits(3:4)));
p.Vertices(4:5,1) = ax.XLim(1);
p.Vertices(2:3,1) = ax.XLim(2);
p.Vertices([1 2 5 6],2) = ax.YLim(1);
p.Vertices(3:4,2) = ax.YLim(2);
p.FaceVertexCData([1 2 5 6]) = ax.YLim(1);
p.FaceVertexCData(3:4) = ax.YLim(2);
end
end
RAJEEV on 1 Jul 2024
Thank You. I also made some changes in the previous code to have better visualization.

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