Is there a way to make a plot of a line with different colors?

If I have y = rand(100,1), can I plot y such that the portions of the line that are greater than or equal to 0.5 is plot in red while portions lying below 0.5 is plot in black?

Answer 1

[Jos (10584)]

To plot lines as well:

% some data
x = linspace(0,1,100);
y = rand(1,length(x));

tf = y >= 0.5 ;
y2 = y ; y2(~tf) = nan ; 

ph = plot(x,y,'k.-',x,y2,'ro-')
set(ph(2),'linewidth',2)

[Floyd Haylock]

Thanks for the responses but none of them provide what I am hoping to achieve. I have attached an image of what I am trying to accomplish. The dotted line in the image would be the 0.5 line. All parts of the curve above 0.5 should be in red; parts of the curve below the 0.5 line should be in black.

[Image Analyst]

I'm not seeing the attachment. Where did you attach it????

[Floyd Haylock]

Sorry. I thought that I had also submitted the attachment. I am re-submitting.

FYI, I went ahead and used the last lines of code that Jos provided but made an edit to it. Here is what I now have and this one seems to be working:

% some data
x = linspace(0,1,100);
y = rand(1,length(x));

x1 = linspace(0,1,5000);
y1 = interp1(x,y,x1);

tf = y1 >= 0.5 ;
y2 = y1 ; y2(~tf) = nan ; 
ph = plot(x1,y1,'k.-',x1,y2,'ro-')
set(ph(2),'linewidth',2)