# LabVIEW

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## Analyzing Graphs

I want to create a graph as in the following example. (example graph is attached)

eg: For each value of 'Vcb' , i want to draw graph between 'Ie' and 'Veb' and have to calculate slope and if the value of slope exceeds some limit,have to change the colour of graph.

Anyone please show an example code for doing this.

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## Re: Analyzing Graphs

What form is your source data in ?

It seems pretty straightforward if you have arrays of {Ie | Veb} for each Vcb you want.

What have you done so far?  What part is giving you trouble?

Steve Bird
Culverson Software - Elegant software that is a pleasure to use.
Culverson.com

Blog for (mostly LabVIEW) programmers: Tips And Tricks

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## Re: Analyzing Graphs

I have not tried. I want to know how to start .

I am acquiring 3 parameters continously : temperature, presssure and volume. For each temperature value i am acquiring i need to draw the graph between pressure and volume.

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## Re: Analyzing Graphs

Hi tomp,

use a XY graph to plot pressure vs. volume.

Create a plot for each temperature.

Done.

Best regards,
GerdW

using LV2016/2019/2020 on Win8.1/10+cRIO
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## Re: Analyzing Graphs

You chose an inaccurate example, then.

For Ie vs. Veb there is no overlap possible ( any X on a plot has one and only one corresponding Y value).  Thus a waveform graph is your best choice.

But if you're doing P-V cards, then any X will have two Y-values (one on compression side, one on discharge side).

You therefore need an X-Y graph, which can handle X-Y pairs.

Your first step should be to take some (possibly simulated) P-V data and plot it on an X-Y graoh.

I would recommend an array of bundles:

[ { V0 | P0 }, {V1 | P1 ], { V2 | P2 }, {V3 | P3 } .... ]

If you have data in that form, then you can wire it directly to an X-Y graph and it plots.

That's the P-V card at one temperature.

Work on that until you get it right and understand it.

Then build an array of TWO of those (different data on each) and wire THAT to the X-Y graph.

You should see TWO P-V cards.  Make them different colors.

Those two will be at different temperatures.

That should get you there - you can plot as many different cards as you wish.

Although, I must not be understanding something - the temperature of the gas inside the cylinder does not stay constant during a compression cycle.  Assuming that it does is a mistake.

PV=nRT is not just a good idea, it's the law.

Then

Steve Bird
Culverson Software - Elegant software that is a pleasure to use.
Culverson.com

Blog for (mostly LabVIEW) programmers: Tips And Tricks

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