How linear regression of -20 dB on the graph?

[G.Orkia]

Hello

 

I'd like to do a linear regression of -20 dB and -30 dB on a graph, could someone tell me how I should go about it?

 

Thank you

[Vincent90]

Hi,

You can try out with Linear Fit.vi or Logarithm Fit.vi

BR,

Vincent

[G.Orkia]

Hi Vincent I tried but I want to make a point of interval on my chart. G.ORKIA

[GerdW]

Hi G.,

I want to make a point of interval on my chart

Just create this point!

Questions as usual:

- What exactly is the problem?

- Mind to attach an example VI?

- How do you want to interpolate? (linear? logarithmic?)

[G.Orkia]

Simply create this point!
The point can vary so how can I do?

Questions as usual:

- What is the problem exactly?
I have a graph with a fall in dB versus time, to be precise in our calculations, I am asked to study the curve with a drop of -5 dB maximum point (initially we have a tray so to -5dB from the tray) and then I have to do a linear regression of all the points for a fall to -20 dB and the exact same thing to -30 dB.

- Spirit of attaching an example VI?
My vi is not yet finished, infact I can not even see my graph because I'm not in good conditions.

- How do you want to interpolate? (Linear? Logarithmic?)
What is interesting to me is the linearity points
.

[GerdW]

Hi G.,

I am asked to study the curve with a drop of -5 dB maximum point (initially we have a tray so to -5dB from the tray) and then I have to do a linear regression of all the points for a fall to -20 dB and the exact same thing to -30 dB.

It REALLY would help when you would attach an image of what you're talking about!

What is interesting to me is the linearity points

What are "linearity points"?

LabVIEW comes with functions for linear regression…

[G.Orkia]

I let as an attachment that I must have.

I have to study the curve at -5 dB of the maximum, so here we consider the curve from only 75 dB, then make a linear regression of 75 dB to 55 dB (-20 dB drop), but also 75 dB to 45 dB (-30 dB drop).
I use linear regression function but I do not see how I can not tell him each time to each point.

thank you very much for your help

[GerdW]

Hi G.,

I do not see how I can not tell him each time to each point.

Linear regression takes X and Y values as input.

So where is the problem to provide your x (=time) and Y (=db values) to this function?

[G.Orkia]

the problem is not at this level, but how it can make a linear regression for only part of the curve. I may have badly worded my question.

[RavensFan]

Do a linear regression on a subset of the array.  Pick the part of the array that is within the limits you want.