R help - May 2007 - Query about finding correlations

Hi
I have a dataframe which has 3 columns of numeric data
A,B,C each of which has been obtained independent of
the other.

We are trying to find out, which of A or B cause C
i.e. We are hypothesising that C is the effect and
either A or B, not both is the cause.

i.e. A causes C and this cause-effect relationship
explains B.

The data for A contains more noise than that for B.
We are working with around 1000 points.

I would greatly appreciate any inputs on the best
statistcal approach to tackle this problem. 
I am thinking that we can find correlation
coefficients between A and C, and between B and C, but
I am not sure this answers the question.
Also we do not know whether the correlation between
them is linear or non linear.

Thanks
Lalitha

Hi
This is not a homework assignment :)
Me and my manager are trying to understand the problem better. In the
meanwhile, we thought we would post the problem on this forum to seek some
input from statisticians who possibly do this kind of analyses everyday and
hence are possibly more proficient with R and/or any recommended
methodologies.

Lalitha

On 5/2/07, Stefan Grosse <singularitaet@gmx.net>
wrote:
>
> How about making your homeworks yourselfes?
>
> lalitha viswanath wrote:
> > Hi
> > I have a dataframe which has 3 columns of numeric data
> > A,B,C each of which has been obtained independent of
> > the other.
> >
> > We are trying to find out, which of A or B cause C
> > i.e. We are hypothesising that C is the effect and
> > either A or B, not both is the cause.
> >
> > i.e. A causes C and this cause-effect relationship
> > explains B.
> >
> > The data for A contains more noise than that for B.
> > We are working with around 1000 points.
> >
> > I would greatly appreciate any inputs on the best
> > statistcal approach to tackle this problem.
> > I am thinking that we can find correlation
> > coefficients between A and C, and between B and C, but
> > I am not sure this answers the question.
> > Also we do not know whether the correlation between
> > them is linear or non linear.
> >
> > Thanks
> > Lalitha
> >
> > ______________________________________________
> > R-help@stat.math.ethz.ch mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
> >
> >
>
>
	[[alternative HTML version deleted]]

Lalitha Viswanath wrote:
> 
> We are trying to find out, which of A or B cause C
> i.e. We are hypothesising that C is the effect and
> either A or B, not both is the cause.
> (...) 
> I would greatly appreciate any inputs on the best
> statistcal approach to tackle this problem. 
> I am thinking that we can find correlation
> coefficients between A and C, and between B and C, but
> I am not sure this answers the question.
> Also we do not know whether the correlation between
> them is linear or non linear.
> 
If the causation (not the correlation) is not linear,
then the correlation (which is linear, always) may not
be the best indicator.

Take, as an extreme case, this:

A <- (-50:50) + 100 * rnorm(101)
B <- abs((-50):50) + 10 * rnorm(101)
C <- A^2 / 50 + rnorm(101)
cor(A, C)
cor(B, C)

A is obviously the "cause" of C, but B (in some cases)
is better correlated to C than A to C.

Alberto Monteiro

How about making your homeworks yourselfes?

lalitha viswanath wrote:
> Hi
> I have a dataframe which has 3 columns of numeric data
> A,B,C each of which has been obtained independent of
> the other.
>
> We are trying to find out, which of A or B cause C
> i.e. We are hypothesising that C is the effect and
> either A or B, not both is the cause.
>
> i.e. A causes C and this cause-effect relationship
> explains B.
>
> The data for A contains more noise than that for B.
> We are working with around 1000 points.
>
> I would greatly appreciate any inputs on the best
> statistcal approach to tackle this problem. 
> I am thinking that we can find correlation
> coefficients between A and C, and between B and C, but
> I am not sure this answers the question.
> Also we do not know whether the correlation between
> them is linear or non linear.
>
> Thanks
> Lalitha
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
>
>
______________________________________________
R-help at stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.