how do I discart the firsts sample readings of my NI and plot the rest in a graph

[altenbach]

Run your VI until the graph contains data. Stop the vi, right click the graph terminal and select "create constant". Save the vi and attach it here.

[anaavilas]

Here it is,
Sorry that it took so long, I had a problem with my pressure transducer.

Hope you can still help me.

What I really want to do is match a cycle of pressure with a cycle of the cossine function in a way that the first value of the pressure is the minimum value of the wave.

[altenbach]

Your diagram constant is empty. Did you run the VI before creating the constant?

[anaavilas]

Yes I did.
I run it, clicked on creat -> constant on the  XYgraph exit (at block diagram) then saved it.

[altenbach]

Right-click on the xy graph terminal labeled "PV diagram" (all the way on the right), not elsewhere. Then make sure the diagram constant is NOT empty.

[anaavilas]

Here it is.

[altenbach]

Here's how to discard the points up to the maxY.

(Of course all you need to do is retain the second plot)

[anaavilas]

This is great.
But it isn`t what I really need.
I need to obtain the data after the maximum point of the pressure (waveform graph)
My PV diagram should have an oval shape.

[anaavilas]

I want the circled data to go to the PV diagram

[altenbach]

What is the t0 and dt for the graph? You need to set that, then just wire the waveform graph as indicated.