obtaining interpolated data from a table

[IñigoP]

Hello to everyone,

I want to enter with the Power data in the table and obtain the value of the speed in rad/s, any suggestions? The thing is that I have 2 points with the same value of power for different speeds because the shape of the plot is a curve.

[pauldavey]

I would try to do a curve fit using a parabola (2nd order polynomial). You could even do it in Excel. Once you have the curve fit function established, you could generate values for any Power.

[GerdW]

Hi Inigo,

two methods to solve your request in LabVIEW:

Both have their disadvantages. And they don't give the same result…

because the shape of the plot is a curve.

Wrong!

YOU made that a "curve" because YOU enabled "plot smoothing" in Excel! You can also show that plot with straight lines between the points…

[IñigoP]

Hi Gerd,

Here you are entering to the table with the speed, in my case I want to enter with the power.

[GerdW]

Hi Inigo,

Here you are entering to the table with the speed, in my case I want to enter with the power.

I took the values from your image - and you already named them "power".

No idea where you got the term "speed" from…

Edit:

You FORGOT to include a proper label in your data table. You should have written "Speed (rad/s)" in the column header! (Didn't your teacher told you how to label data tables/graphs scientifically correct?)

"Not as simple as it is" solution: just switch X and Y arrays/columns in my suggestion!

The Interpolate1DArray method will fail for certain power inputs (read it's help!), but the polynom interpolation will still work as intended.

[IñigoP]

Thank you Gerd and I am sorry for not defining the table properly.

I also thought about dividing the data in two arrays, the first one with the data from 0 rad/s until the speed where the power is the maximum (Vpmax) and the other one with the data from Vpmax to 50 rad/s.

[GerdW · Accepted solution]

Hi Inigo,

yes, that would help to use Interpolate1DArray.

But you need to keep track of the actual "position" of the power to always know which side of the parabola to calculate!