# Re: FW: lspoly didn't wok when the number of data points equal to the number of coefficients

From: Dennis Shea <shea_at_nyahnyahspammersnyahnyah>
Date: Mon Dec 30 2013 - 09:35:37 MST

The Description section documentation was not correct. It has been changed.

On 12/29/13, 9:53 AM, Richard Liang wrote:
> Thanks, Dennis
> The document said "It is necessary that the number of data points) be greater than or equal to n(the number of coefficients)."
> As I understand , for example, if I have 3 points, the max number of coefficients can be 3.
> Mathematically, if I have 3 points, I can make an secend order polynomial to fit these points , in which I should have 3 coefficients.
>
> Best
>
>> Date: Sat, 28 Dec 2013 08:26:49 -0700
>> From: shea@ucar.edu
>> To: richardljy@hotmail.co.uk; ncl-talk@ucar.edu
>> Subject: Re: FW: lspoly didn't wok when the number of data points equal to the number of coefficients
>>
>> As noted in the documentation:
>>
>> n
>>
>> The number of coefficients desired (i.e., n-1 will be the degree of the
>> polynomial). Due to the method used, n should be less than or equal to
>> five.
>>
>> ===
>>
>> In your case with 3 points, the max number of coefficients would be 2
>>
>>
>> On 12/28/13, 5:01 AM, Richard Liang wrote:
>>>
>>>
>>> From: richardljy@hotmail.co.uk
>>> To: ncl-talk@ucar.edu
>>> Subject: lspoly didn't wok when the number of data points equal to the number of coefficients
>>> Date: Sat, 21 Dec 2013 15:45:08 -0500
>>>
>>>
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>>> lspoly didn't wok when the number of data points equal to the number of coefficientsI did the test
>>> x = (/-4.5, -3.2, -1.4/)y = (/ 0.7, 2.3, 3.8/)n = 3 c = lspoly(x,y, 1, n) print(c)c will be(0) 1e+20(1) 1e+20(2) 1e+20
>>>
>>>
>>> But if n=2 c will be(0) 5.268707(1) 0.9896836
>>> I also did the test in the 4 element array, when n=4, it didn't work. only when n is less than the number of data points
>>> Any body help me? thanks
>>>
>>>
>>>
>>>
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>
>
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Received on Mon Dec 30 09:35:49 2013

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