Re: Re: Re: Mathematica function to calculate correlation coefficient?
- To: mathgroup at smc.vnet.net
- Subject: [mg108190] Re: [mg108131] Re: [mg108094] Re: Mathematica function to calculate correlation coefficient?
- From: DrMajorBob <btreat1 at austin.rr.com>
- Date: Wed, 10 Mar 2010 01:44:49 -0500 (EST)
- References: <hmvq80$17c$1@smc.vnet.net> <201003081113.GAA03974@smc.vnet.net>
- Reply-to: drmajorbob at yahoo.com
The data doesn't have to be "close" to have a high correlation; it has to
be "nearly parallel".
t and 10^7+t are perfectly correlated, for instance.
Bobby
On Tue, 09 Mar 2010 12:41:34 -0600, Yun Zhao <yun.m.zhao at gmail.com> wrote:
> Would Correlation[ ] still work if n(t) and the actual data points were
> not
> linear functions of time? By that, I mean, n(t) is something like
> C1*exp(rate*t)+C2. I am asking because in one case, where I think I have
> some errors in my data, n(t) does not come close to any of the data
> points,
> it is far apart, and Correlations [ ] gives me 0.97.
>
> On Tue, Mar 9, 2010 at 12:27 PM, DrMajorBob <btreat1 at austin.rr.com>
> wrote:
>
>> If n is a InterpolationFunction returned by NDSolve or a symbolic
>> function
>> returned by Solve, n[t] is obviously not a list of 8 values; it's one
>> value
>> for each t.
>>
>> You can create such a list, of course, with, for instance, Array[n,8] or
>> n/@{.1,.3,.4,.8,.9,1.2,...} (any list of eight t values).
>>
>> Once you have a pair of same-length lists, Correlation will calculate
>> what
>> the name says.
>>
>> Bobby
>>
>>
>> On Tue, 09 Mar 2010 05:20:19 -0600, Yun Zhao <yun.m.zhao at gmail.com>
>> wrote:
>>
>> Thanks for your reply. But remember, the set of data values is 20 data
>>> points, and my computed distribution of n(t) is a function of t, so
>>> thousands and thousands of points. When I tried to use
>>>
>>> Correlation[data1, n(t)]
>>>
>>> I get the error "Correlation::vctmat: The arguments to Correlation are
>>> not
>>> a
>>> pair of vectors or a pair of matrices of equal length." Please tell me
>>> what
>>> I did wrong. Thank you.
>>>
>>> Correlation::vctmat: "
>>>
>>> StyleBox[\"\"\", \"MT\"] The arguments to Correlation are not a pair of
>>> vectors or a pair of matrices of equal length
>>>
>>>
>>> On Mon, Mar 8, 2010 at 5:13 AM, Sjoerd C. de Vries <
>>> sjoerd.c.devries at gmail.com> wrote:
>>>
>>> Surprisingly, you can use the function Correlation to calculate the
>>>> correlation between two lists. In your case you should probably use
>>>> the set of predicted values and the sat of actual data values.
>>>>
>>>> Cheers -- Sjoerd
>>>>
>>>> On Mar 7, 11:05 am, Yun Zhao <yun.m.z... at gmail.com> wrote:
>>>> > Hi everyone,
>>>> >
>>>> > I solved a differential equation, and got a solution n(t). Now I
>>>> have
>>>> > collected 8 data points at 8 different times. I plotted the
>>>> solution
>>>> of
>>>> > n(t), and the curve intersect the 8 data points quite well on a
>>>> graph
>>>> of
>>>> > n(t) vs. t. How do I use Mathematica 7.0 to calculate the
>>>> correlation
>>>> > coefficient R^2 value of how well the n(t) solution fit the data
>>>> points?
>>>> > Thank you very much.
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>
>> --
>> DrMajorBob at yahoo.com
>>
--
DrMajorBob at yahoo.com
- References:
- Re: Mathematica function to calculate correlation coefficient?
- From: "Sjoerd C. de Vries" <sjoerd.c.devries@gmail.com>
- Re: Mathematica function to calculate correlation coefficient?