Ugly Lines in Plot

I am plotting joint angles while walking (multiple steps). I have two vectors, joint angle and percent of step. When I plot:

plot(percent,angle)

MATLAB plots my data but I have ugly horizontal lines across my plot connecting adjacent steps.

In the past I would separate steps with NaN's... but there has to be a easier way... What is the simplest way to get rid of these lines? Thanks ~Dan

[Walter Roberson]

Separating them with NaN is the easiest way.

Answer 1

[Image Analyst]

If you want to find out where the backtracking happens, you can use diff(). Then just extract out the sections of the curve in-between the backtrack locations into separate arrays and plot them. If you want a demo, here's one:

% Generate some sample data.
index = 1;
for p = 1 : 15
  oneX = 1:100;
  x(index:index+99) = oneX;
  sigma = 20 * rand(1);
  r = oneX .* exp(-(oneX.^2)/(2*sigma^2))/sigma^2 + rand(1);
  rayleigh(index:index+99) = r;
  plot(x, rayleigh, 'r-', 'LineWidth', 2);
  hold on;
  grid on;
  index = index + 100;
end
ylim([-.2 1]);
title('Plot with back tracking', 'FontSize', 20);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);

%===============================================
% Now we have some sample data and we can begin.
%===============================================

% Find out where x reverses direction
dx = diff(x);
startingXs = find(dx<0)+1;
% Add the first element.
startingXs = [1 startingXs];
% Now we have our starting x's.
% Let's plot the curves one at a time.
figure;
for p = 1 : length(startingXs)
  oneCurveX = x(startingXs(p):startingXs(p)+99);
  oneCurveY = rayleigh(startingXs(p):startingXs(p)+99);
  plot(oneCurveX, oneCurveY, 'b-', 'LineWidth', 2);
  hold on;
  grid on;
end
ylim([-.2 1]);
title('Plot without back tracking', 'FontSize', 20);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);

[Daniel]

This answers my question... I was really hoping that there was a simpler/shorter way to do this... Thanks

[Image Analyst]

Without generating the sample data and without all the comments and other fluff, essentially it's only about 7 or 8 lines of code.

Answer 2

[Amarpal]

Perhaps you are talking about the gridlines? You can use the following: h = plot(percent,angle); set(h,'edgecolor','none')

Hope this is what you were looking for?

[Daniel]

No... but thank you for trying... maybe this will help...

I want to get rid of straight lines that go back across the plot connecting adjacent steps...

[Andrea]

probably you should plot them as different function. One more thing that came to my mind is using plot(x,y,'.'). In this way you can get ride of lines at all.