MATLAB: Change plot color for increasing or decreasing x values

data importplotting

Hi all…I'm pretty inexperienced with MATLAB so bear with me. I am trying to import a data set from a .txt file which has many cycles along the x-axis. Since the x-axis is temperature, I would like the increasing segment of each cycle curve (heating) to be red and the decreasing segment (cooling) to be blue. I'm not experienced enough to write a FOR loop to implement this, and I was unable to find a solution on the forums. Any help is much appreciated. Thanks!

Best Answer

from what you described you don't really need a for loop to implement it. here is a solution to get away from a for loop
 %my attempt to make something i think you're plotting.  
 %something like a Hysteresis curve.  
  y = [0 8 12 8 0 -8 -12 -8  0];
  x = [2 10 10 8 -2 -10 -10 -8 2];
  figure,plot(x,y)
 %find which segments are heating and cooling or staying the same.  
  dx = diff(x); %takes x(n+1)-x(n) 
  heating = dx>0; %positive dx
  steady = dx ==0; %0 dx (temp values didn't change) 
  cooling = dx<0;  %negative dx.
plotSegmentX = [x(1:end-1);x(2:end)];  %pair the segments up.  

plotSegmentY = [y(1:end-1);y(2:end)];  %pair the segments up.  
%plot only the heating segments and color them red. then plot only the cooling etc.
figure,plot(plotSegmentX(:,heating),plotSegmentY(:,heating),'r',...
    plotSegmentX(:,cooling),plotSegmentY(:,cooling),'b',...
    plotSegmentX(:,steady),plotSegmentY(:,steady),'g')
xlim([-14 14]);ylim([-12 12])
Related Question