Hello,

Asking help for homework is prohibited on this list.

Regards,
Pascal


2013/9/19 Guy Wachsman <guy.wachsmann@duke.edu>

>  Hi Pascal,
>
>  The first reason is that it was a homework assignment, the second it
> that this function is based on the algebraic equation for correlation
> matrix (given to us by the instructor, not my initiative) and to me (and
> probably to others) it is nice to see the correlation.
>
>  Cheers,
> Guy
>
>    --
> Guy Wachsman
> Benfey lab, FFSC #4131, Duke
> 130 Science Drive
> 27708, Durham, NC
> email: gw57@duke.edu
>
>      ------------------------------
> *From:* skalp.oettli@gmail.com [skalp.oettli@gmail.com] on behalf of
> Pascal Oettli [kridox@ymail.com]
> *Sent:* Wednesday, September 18, 2013 8:20 PM
> *To:* wacguy
> *Cc:* r-help
> *Subject:* Re: [R] cov2cor exp
>
>    Hello,
>
>  I am just wondering why to reinvent the wheel?
>
>  Regards,
>  Pascal
>
>
> 2013/9/19 wacguy <gw57@duke.edu>
>
>> Ok, Thanks foe the answer, Ken:
>>
>> *1L, 2L etc are integers. (That is, identical to as.integer(1) ,
>> as.integer(2) etc)
>>
>> Using integers (instead of "numeric" type) is more efficient as here
>> they're
>> used as indexes and would be converted to integer anyway.
>>
>> Compare
>> > is(1)
>> ... and
>> > is(1L)
>>
>> 1L:p is the sequence 1, 2, 3, ..., p (just like 1:p)
>>
>> Just for curiosity, what is findFn('cov2cor') ?
>>
>> Regards,
>> Kenn*
>>
>> I don't know what findFn('cov2cor') is, I'm a total newbie to R but I
>> created a new, simpler to my opinion function for some descriptive
>> statistics as matrix functions for a matrix called "x":
>>
>> one1=c(rep(1, nrow(x)))
>> means <- t(one1)%*%x/3#row vector of means
>> M=one1%*%means#A 𝑛 × 𝑝 matrix 𝑀 where each column is filled with the
>> mean
>> value for that column
>> D=x-M#deviation matrix
>> S=(t(D)%*%D)/(nrow(x)-1)#Covariance matrix
>>
>> R=function(S){###R is a Correlation matrix###
>>   V=matrix(nrow=nrow(S),ncol=ncol(S))
>>   V1 <- sqrt(1/diag(S))
>>   diag(V)=V1
>>   V[is.na(V)]=0
>>   R=V%*%S%*%V
>>   return(R)
>> }
>>   R(S)
>>
>>
>>
>> --
>> View this message in context:
>> http://r.789695.n4.nabble.com/cov2cor-exp-tp4676395p4676450.html
>> Sent from the R help mailing list archive at Nabble.com.
>>
>> ______________________________________________
>> R-help@r-project.org 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.
>>
>
>
>
>  --
>  Pascal Oettli
> Project Scientist
> JAMSTEC
>  Yokohama, Japan
>



-- 
Pascal Oettli
Project Scientist
JAMSTEC
Yokohama, Japan

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