When you use plot() without hold(‘on’), each new plot() clears the axes and draws a new line, so your second plot() of p2 caused the first plot() line (p1) to be erased.
Add a call to hold(‘on’) before you plot to ensure that both lines are ploted and not deleted.

x = linspace(0,4*pi,150);
y1 = sin(x);
y2 = 1/10*sin(x);
p1 = plot(x,y1);
p2 = plot(x,y2);

cd1 = colormap('parula');  %color code for y1
cd1 = interp1(linspace(min(y1),max(y1),length(cd1)),cd1,y1); 
cd1 = uint8(cd1'*255); % need a 4xN uint8 array
cd1(4,:) = 255; % last column is transparency

cd2 = colormap('parula');  %colorcode y2
cd2 = interp1(linspace(min(y1),max(y1),length(cd2)),cd2,y2); %uses the same scaling as cd1  
cd2 = uint8(cd2'*255); % need a 4xN uint8 array
cd2(4,:) = 255; % last column is transparency

P={p1.Edge;p2.Edge}; %not sure how this works
NameArray={'ColorBinding','ColorData'};
ValueArray={'interpolated','cd1';'interpolated','cd2'};
drawnow
set(P,NameArray,ValueArray)

I am getting the error messages.

Invalid or deleted object.
Error in trialv4 (line 20)
P={p1.Edge;p2.Edge};

Sorry for the lengthy post. Thanks!

@Ben – it looks perfectly ok (with color gradient and all) on my R2022a… Perhaps you missed some of the steps (e.g. setting the ColorBinding to 'interpolated') or perhaps you do not have a drawnow/pause before you modify the displayed line (i.e. you try to modify the line before Matlab has completed its on-screen rendering).

Any chance there is a fix?

There is no Edge in quiver, so this workaround will not help.

Take a look at this function, it fades a plot and add new data on it.
https://www.mathworks.com/matlabcentral/fileexchange/69816-fadeit

Hi Yair,

There is an issue when there are too many points in the plot as Sebastian pointed out above. Below 25000 points, everything works as expected:

% define
N   = 25000;
t   = linspace(0,4*pi,N);
x   = 27*cos(t) + 29*cos(27/2*t);
y   = 27*sin(t) - 29*sin(27/2*t);

% plot
hFig  = figure('Units','normalized','Position',[0.2 0.2 0.4 0.5]);
hAxes = axes('XTick',{},'YTick',{},'NextPlot','replacechildren','Box','on');
hPlot = plot(x,y);
axis equal tight;
drawnow(); % as required
%
hPlot.Edge.ColorBinding = 'interpolated';
hPlot.Edge.ColorData    = [uint8(parula(N)*255) 255*ones(N,1,'uint8')]';

Above this magic number, Matlab tries to optimize the figure by plotting only a subset of the vertices. Repeating the procedure with more points than that results in a warning and no color gradient:

N   = 25001;
...
hPlot.Edge.ColorData    = [uint8(parula(N)*255) 255*ones(N,1,'uint8')]';

Warning: Error creating or updating LineStrip
 Error in value of property  ColorData
 Array is wrong shape or size 

To fix the issue, we need to probe the number of vertices in hPlot.Edge:

N   = 25001;
...
N2  = size(hPlot.Edge.VertexData,2);
hPlot.Edge.ColorData = [uint8(parula(N2)*255) 255*ones(N2,1,'uint8')]';

But, if we try, say, to resize the figure, the warning reappears (though the gradient stays):

drawnow(); % just in case...
hFig.Position = [0.2 0.2 0.5 0.6];

Warning: Error creating or updating LineStrip
 Error in value of property  ColorData
 Array is wrong shape or size 

Similar unexpected behavior occurs in zoom, copyobj etc.

P.S, my Matlab version is R2018a, so it looks like a rather persistent problem.

I am trying to plot a line with a gradient which would be “perpendicular” to the line. For example:

N = 10;
p = plot(1:N, ones(1, N), ‘Linewidth’, 20);
cd = [uint8(jet(N)*255) uint8(ones(N, 1))].’;
drawnow
set(p.Edge, ‘ColorBinding’,’interpolated’, ‘ColorData’,cd)

This is a horizontal line with color gradient going from left to right (in the direction of the sample points). Is there a way to have a gradient going from top to bottom? (if the line is tilted, then the gradient would be still perpendicular to that line). The effect should look like the line is fading out in the perpendicular direction.

Thanks for any hints and ideas.