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matlabcolorstime-seriesmatlab-figure

Plotting one time-series in different colors matlab

I would like to reproduce the following plot in MATLAB:

enter image description here

For instance, consider the following time series:

a= [1,0.5,0.25, -0.5, -0.75,0.5,1.25, -0.8,0.1,0.2,0,3,0.8, -0.9, -1,1]

How can I plot values above 0 in one color and values below another color?

Solution

  • The trick is to avoid the plotting of points by replacing their values by NaN.

    I suggest to first separate a in two arrays, lets say a_lo and a_hi.

    • a_lo is a but with positive values replaced by NaN.
    • a_hi is a but with negative values replaced by Nan.

    So you will do something like this:

    a_lo = a;
a_hi = a;

for i = 1:length(a)
    if a_lo(i) > 0
        a_lo(i) = NaN;
    end
    if a_hi(i) < 0
        a_hi(i) = NaN;
    end
end

    Then you plot a_lo and a_hi with different colours, don't forget hold on to plot the two curves together.

    plot(a_lo,'r'); hold on;
plot(a_hi,'b');

    Here is an example of what I could obtain with a sine wave:

    sine wave