Singular Matrix Error

[Molly Rockstroh]

I'm getting the singular matrix error when performing a SinReg in DataQuest on the Nspire.  I read a 2011 thread that suggested I add an initial period, but I don't want to send my data to a spreadsheet to make the fix.  I've done this hundreds of times through the years and have never gotten this error.  Any suggestions?

[Sean Bird]

I've got that kind of error for sine regressions many of times. My recommendation would be to limit the data by either selecting the data and then doing the curve fit, or by striking some of the data. I like the first option best.

If you attached the file, we could take a look.

On Mon, Feb 27, 2017 at 12:13 PM, Molly Rockstroh <mrock...@depere.k12.wi.us> wrote:

I'm getting the singular matrix error when performing a SinReg in DataQuest on the Nspire.  I read a 2011 thread that suggested I add an initial period, but I don't want to send my data to a spreadsheet to make the fix.  I've done this hundreds of times through the years and have never gotten this error.  Any suggestions?

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Sean Bird
AP Calculus & Physics,
NHS Adviser & Rocket Team Supervisor
Math & Science Technology Coordinator
Covenant Christian High School
7525 West 21st Street
Indianapolis, IN 46214
Phone: 317/390.0202 x104 Fax: 317/390.6823
Website: http://covenantchristian.org/bird
work Email: sean...@covenantchristian.org
personal Email: covena...@gmail.com
Psalm 111:2 “Great are the works of the LORD, studied by all who delight in them.”

[Molly Rockstroh]

I tried limiting the data and it still didn't work.  It did when I sent it to a spreadsheet and put a period of 2pi, as John suggested.  But I've never had to do that before.  Thanks for taking a look!

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[Karl]

HI Molly and Sean,
I have been having the same issues, doing the same (or a similar lab).  One thing that "solved it was to have students do the data collection over with a new Nspire document.  No idea why that worked.  A second solution is to copy and paste the data into a LoggerPro file, if you happen to have that Vernier software.  See attached screenshot.

See you in Chicago,
Karlheinz

On Tuesday, February 28, 2017 at 6:19:42 PM UTC-5, Molly Rockstroh wrote:

I tried limiting the data and it still didn't work.  It did when I sent it to a spreadsheet and put a period of 2pi, as John suggested.  But I've never had to do that before.  Thanks for taking a look!

On Mon, Feb 27, 2017 at 11:56 AM, Sean Bird <covena...@gmail.com> wrote:

I've got that kind of error for sine regressions many of times. My recommendation would be to limit the data by either selecting the data and then doing the curve fit, or by striking some of the data. I like the first option best.

If you attached the file, we could take a look.

On Mon, Feb 27, 2017 at 12:13 PM, Molly Rockstroh <mrock...@depere.k12.wi.us> wrote:

I'm getting the singular matrix error when performing a SinReg in DataQuest on the Nspire.  I read a 2011 thread that suggested I add an initial period, but I don't want to send my data to a spreadsheet to make the fix.  I've done this hundreds of times through the years and have never gotten this error.  Any suggestions?

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Sean Bird
AP Calculus & Physics,
NHS Adviser & Rocket Team Supervisor
Math & Science Technology Coordinator
Covenant Christian High School
7525 West 21st Street
Indianapolis, IN 46214
Phone: 317/390.0202 x104 Fax: 317/390.6823
Website: http://covenantchristian.org/bird
work Email: sean...@covenantchristian.org
personal Email: covena...@gmail.com
Psalm 111:2 “Great are the works of the LORD, studied by all who delight in them.”

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[Molly Rockstroh]

Thanks so much, Dave and Sean and Karl.  I hadn't had any luck with Sean's suggestion of limiting the data.  Nor did I have luck with opening a new document.  BUT, when I opened a new document AND limited the domain it worked!  

It also works when I enter an initial period after sending the data to a spreadsheet, as Dave suggested.  But since I have kids performing many regressions until they obtain a given frequency, I really want to do it in DataQuest.  Anyway, at least I can do that now consistently.  So thank you!

In the meantime, I've been in contact with tech support and every suggestion they gave me was one I had already tried.  So I asked if the question could be forwarded to a programmer.  My question was not how to enter a period from DataQuest, it was how I fix the problem to begin with.  Why does  it work sometimes and not others?  Here is the response😊

Hello Molly,

Thank you for your reply. I have discussed the issue with a senior member of our software team. You are correct that there is a way to perform the Sin Regression directly from the data plotted from DataQuest by selecting the following options:

[Menu] [4:Analyze] [6:Curve Fit] [8:Sinusoidal]

This should automatically graph the curve, if it can be done automatically. However, if the above steps result in the singular matrix error using the data that has been collected, I regret to inform you that there is no way to enter a period using this curve fit option. I will be glad to forward the information regarding you having experienced this error to our development team, where they can review the possibility of strengthening this feature in a potential future release.

I hope that you find this information helpful. If you have further questions or comments, please feel free to send me an email.

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[dwi...@lufkinisd.org]

Molly,

I do not entirely understand your question, so I hope the information I give isn't totally irrelevant...

I teach physics, and beginning in OS 4.3, If I sent out a document with a pre-inserted Dataquest page, it malfunctioned.  We reported it and that was about it.  I have not checked yet in 4.4 to find out if pre-inserted DQ pages work again or not.  I just started having the students add them in and adjust the settings themselves. 

I hope that is helpful.  If it doesn't relate to your question, apologies. 

David

[Molly Rockstroh]

Thanks so much for your input, David.  I hadn't sent a doc to the kids, just having them open the DataQuest app themselves.  I'm wondering if it might be a newer OS issue since I never experienced it before.  But thank you, Everyone, I learned a lot.

This is a staff email account managed by Lufkin Independent School District .  This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the sender.

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[Sean Bird]

Let me recommend using Menu > Analyze > Model

If students want more precision, they could right-click (ctrl menu) and change the spin increment. With this they can even type in values for the frequency.

Notice that the model is a modification of the last choice. I wanted c to be the vertical shift, and f to be the frequency. I got a starting frequency by taking the number of cycles dividing it by the time of 0.03seconds.

Sean Bird

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[Molly Rockstroh]

Sean, that's awesome, thank you so much!  I gave my presentation on Saturday and all went well, only a couple singular matrix errors and those we were able to fix.  But this is much more efficient than what I was doing, I will use this in the future.  I really appreciate you taking the time to look at this again, that's awesome!!!