Display Glitch: Overlay of plots don't display requested LineStyle

Hello all,

I'm displaying some data in a particular way and am running into a very strange display glitch. The requested 'LineStyle' property using the plot function is being overwritten/ignored when called multiple times in a for loop. I have prepared a script that reproduces the issue. Please change the "iterationNum" variable to see the issue persist. I'd appreciate intuition on the origin of this issue or work-arounds people find, ideally without resorting to a case-by-case post-correction.

I am using MATLAB version 2023a.

% The bug: lines stop plotting as requested on certain iterations
% MATLAB Version R2023a
% Variable to change: Try 2, 3, 5, 8
iterationNum = 8;

% Less important variable: used for displaying
spacerVal = 10;
alphaVal = 0.2;
xData = 0:25;
testMeans1 = spacerVal/2*rand(size(xData));
testSTDs1 = spacerVal/2*rand(size(xData));
testMeans2 = spacerVal/2*rand(size(xData));
testSTDs2 = spacerVal/2*rand(size(xData));
% Display lines for shifting
shiftBases = ((1:iterationNum)-1)*spacerVal;
[xBG,yBG] = ndgrid([xData(1) xData(end)],shiftBases);
figure
plot(xBG,yBG,'black');
hold on

% Loop over iterations and plot; use breakpoints or ginput() if you want to
% pause
for index = 1:iterationNum
    currColor = [index/iterationNum 0 (1-index/iterationNum)];
    yyaxis 'left'
    plotMeanStdPoly(testMeans1+shiftBases(index),testSTDs1,xData,currColor,alphaVal);
    yyaxis 'right'
    plotMeanStdPoly(testMeans2+shiftBases(index),testSTDs2,xData,currColor,alphaVal);
end

function [] = plotMeanStdPoly(meanVals,stdVals,xVals,currColor,alphaVal)
%PLOTMEANSTDPOLY Sloppy bundle function to plot meanVals with a bounding
%polygon of +/- stdVals.

% Generate a polynomial for background standard deviation
[stdPolyX,stdPolyY] = getPolyCoords(meanVals,stdVals,xVals);
nonanLogic = ~isnan(stdPolyY);
currPoly = polyshape(stdPolyX(nonanLogic),stdPolyY(nonanLogic));

% Plot
polyPlot = plot(currPoly);
hold on
polyPlot.FaceAlpha = alphaVal;
polyPlot.EdgeColor = 'none';
polyPlot.FaceColor = currColor;
plot(xVals,meanVals,'Color',currColor,'LineWidth',2,'LineStyle','--')

end

function [outXs,outYs] = getPolyCoords(yCoords,yHeights,xCoords)
%GETPOLYCOORDS Takes in a set of y-coordinates, y-heights, and optional 
% x-coordinates. Returns a set of coordinates that coorespond to a
% polynomial whose vertices are y-coordinates +/- y-heights at each
% corresponding x-coordinate. Used for plotting standard deviations over
% means.

% Define xCoords, if not passed
if nargin == 2
    xCoords = 1:numel(yCoords);
end

% Generate x-coordinates by reflecting
outXs = [xCoords(:); flipud(xCoords(:))]';

% y-coordinates go +height one way and -height the other way
outYsPlus = yCoords + yHeights;
outYsMinus = yCoords - yHeights;
outYs = [outYsPlus, fliplr(outYsMinus)];

end

Thanks!

[Walter Roberson]

The only getPolyCoords I can find is some python code at https://stackoverflow.com/questions/55659835/trying-to-separate-polygon-data-into-x-and-y-coordinates-but-get-error-multip

[Remi Boros]

Hi Walter,

Thanks for the quick response. I've updated my post to include the relevant function.

Thanks!

Answer 1

[Voss]

Looks like the problem is that yyaxis() changes certain axes properties, including ColorOrder and LineStyleOrder:

figure()
ax = gca();

Axes properties before calling yyaxis():

ax.ColorOrder

ans = 7×3

0 0.4470 0.7410 0.8500 0.3250 0.0980 0.9290 0.6940 0.1250 0.4940 0.1840 0.5560 0.4660 0.6740 0.1880 0.3010 0.7450 0.9330 0.6350 0.0780 0.1840

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ax.LineStyleOrder

ans = '-'

Axes properties after calling yyaxis():

yyaxis left

ax.ColorOrder

ans = 1×3

0 0.4471 0.7412

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ax.LineStyleOrder

ans = 7x2 char array
    '- '
    '--'
    ': '
    '-.'
    'o-'
    '^-'
    '*-'

Then plot() cycles through LineStyleOrder each time it is called, apparently respecting the LineStyle from the line spec you used in the plot() call (which is always '--'), but evidently also using the marker from the axes LineStyleOrder. E.g., in this case the first four rows of ax.LineStyleOrder are specifications without a marker, then rows 5-7 have markers, then the cycle repeats, and those are the markers you see in the plotted lines.

N = 10;

x = 0:9;
y = 0:9;

hold on

for ii = 1:N
    
    y = y+1;
    plot(x,y,'LineStyle','--')
    
end

[Remi Boros]

Thank you for the thorough investigation. This is good to know for the future!

Answer 2

[Remi Boros]

Hello all,

I realize that the problem I'm running into is related to the 'Marker' property, not 'LineStyle.' By setting 'Marker' to 'none' the problem is solved. Still: I would appreciate any intuition as to why MATLAB chooses to display Markers in some instances and not others.

Thank you all!