MATLAB: Plot with step changes – no interpolation

line styleplottingstep change

Hello,

The standard for plotting a line in matlab is that the line is drawn with a constant slope between the points. I would like to plot something where each subsequent y-value represents a step change in rate. The resulting plot would look blocky, rather than smoothed between the points. Any suggestions that will help me with this?

Thank you.

Best Answer

stairs(1:10)

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How about using interp1 with the 'pchip' option? You did speculate the interpolation is overly complex, but then again it is only one line in Matlab.

First I generate some (fake) data similar to what you have shown.

y = @(x) 320*(1+tanh(x-5));
x = linspace(0,8)';
Ts = 1; % [s] 
xi = [0:Ts:8]'; 
[xs,ys] = stairs(xi, y(xi))
plot(x,y(x), xs, ys, xi, y(xi), 'rs')

Now the ZOH sample & held data is (xi, y(xi)). Using only this data, we reconstruct the higher density data with interp1.

Ts2 = Ts/10; 
xi2 = [0:Ts2:8]'; 
yq = interp1(xi, y(xi), xi2, 'pchip'); 
plot(xi, y(xi), 'rs', xi2, yq, 'b-')

I use the pchip option to avoid "wobbles" in the interpolation.

MATLAB: Interpolation

You probably need to use interp1. If you can post your code, I can maybe be more specific.

HTH,

Arnaud

Best Answer

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MATLAB: Interpolation

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