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Re: FFT function

Jeff_Perkinson

Let’s try the JMP SE community (cc’d) to see what help we can find there.

Jeff Perkinson

JMP Customer Care Manager

SAS Institute Inc.

SAS Campus Drive • Cary, North Carolina 27513 • USA

Ph: 919-531-6521

E-mail: Jeff.Perkinson@jmp.com<mailto:Jeff.Perkinson@jmp.com>

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On Oct 8, 2015, at 10:10 PM, Bill Worley <Bill.Worley@jmp.com<mailto:Bill.Worley@jmp.com>> wrote:

Hey Guys,

Please take a look at the request below from one our customers. I no experience with FFT and JMP.

Thanks,

Bill

From: Putnam, Thomas R. (Tom)

Sent: Thursday, October 08, 2015 5:02 PM

To: Bill Worley <Bill.Worley@jmp.com<mailto:Bill.Worley@jmp.com>>

Subject: FFT function

Bill,

I hope you can help me with attempting to analyze the attached data using FFT.

If you run the scripts, you can perhaps see there are two modes.

This is a round part that has some ovality. I was hoping to use FFT to quantify this in some parametric manner so that I could apply to other parts for comparison.

I see that FFT requires a matrix, but I’m unclear about the output and interpretation.

Help??!!

Tom Putnam

tom.putnam@timkensteel.com<mailto:tom.putnam@timkensteel.com>

Business Process Improvement Technologist

Desk: 330-471-6626 Cell: 330-323-8345

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This message and any attachments are intended for the individual or entity named above. If you are not the intended recipient, please do not forward, copy, print or disclose this communication to others; also please notify the sender by replying to this message, and then delete it from your system. TimkenSteel Corporation

Message was edited by: Jeff Perkinson

Attachment removed. Bill says the data are proprietary.

Accepted answers

All comments

martindemel

Hi Bill,

besides using the Scripting functionality to run an fft with MATLAB I believe Dan V. has some example on how to do this, but I do not remember what exactly The first I guess was this blog post: How to use JMP and MATLAB together

Regards,

Martin

Byron_JMP

for FFT help, take a look at this internal link: http://sww.sas.com/jmpmediawiki/JSLFFT_Function

Bill_Worley

Byron,

Thanks for your reply. Maybe a little naive here, but is this okay to share with a customer?

Best,

Bill

Daniel_Valente

billw@jmp -- this Add-In from Bill Fish may be something you'd be interested in forwarding to your customer: JMP Addins for Frequency Analysis and Dual Seasonality Time Series Analysis https://community.jmp.com/docs/DOC-6994

Bill_Worley

Thanks Dan. I will the add-in with our customer.

yusuke_ono

It might be easy to interpret results by cos and sin functions, not by Euler's expression or complex numbers.

The linked PDF file explains how to transform FFT's results to coefficients for sin and cos functions.
The linked script shows the interpretation in terms of sin and cos functions.

https://community.jmp.com/docs/DOC-9294

https://community.jmp.com/docs/DOC-9295

Nate_Riordan

Resurrecting this thread a bit.

Just had a similar question come from a customer. Anybody have a good explination as to why Matlab's FFT and JMP's spectral density would come up with different values?

Screen Shot 2017-04-24 at 6.26.43 PM.png

Daniel_Valente

Nate --

You have to zoom into the left graph to find out how many periods are at the frequency of the peak.

The data set is sampled at 2000 Hz.

t = 1/f.

t = 12.585 periods * .0005s (1 sample) = .0062925.

.0062925 = 1/f. f = 158.9 Hz.