Integration of Numeric Data in cycle

Hello.

I have a data set that represents the cycle of a compressor. In the X axis is the volume and in the Y axis is the Pressure.

We know that the area inside of the cycle represents the Work done by the compressor.

How could I get this area (integral of discrete points) in MATLAB?

I already read this document: https://www.mathworks.com/help/matlab/math/integration-of-numeric-data.html

and applied this command line: Area = trapz(Pressure)

The output that I received is: Area = 3.2682e+03

Is that the correct approach?

I am attachin the plot.

Answer 1

[Torsten]

Work on your data first so that you get a closed, non-overlapping curve. Especially "clean" the upper and the right part. Then apply "polyshape" and "area" or "polyarea".

But you should check for plausibility by looking at the graph.

r = 1;
phi = 0:2*pi/100:2*pi;
x = r*cos(phi);
y = r*sin(phi);
s = polyshape(x(1:end-1),y(1:end-1))

s = 
  polyshape with properties:

      Vertices: [100×2 double]
    NumRegions: 1
      NumHoles: 0

a1 = area(s)

a1 = 3.1395

a2 = polyarea(x,y)

a2 = 3.1395