# [R] correlation with boot

ctu at bigred.unl.edu ctu at bigred.unl.edu
Tue Sep 2 07:49:17 CEST 2008

```Hi Professor Ripley,
(Thank you very much)^infinite for your response. I still have few questions
1. R shows that I have two column in nlaw data.
> ncol(nlaw)
[1] 2
> corr(nlaw)
[1] 0.7763745
2. Why can't I use boot::corr? I check corr in boot package and it
seems to be used for computing correlation coefficient,right?
3. The last question, cor is for computed the correlation variance and
covariance matrix. Would you give a explanation for
cor(data[ind,])[1,2]
I do not get it.

Appreciate,
Chunhao

Quoting Prof Brian Ripley <ripley at stats.ox.ac.uk>:

> Please look at the help for boot, in particular what it says the form
> of 'statistic' should be.  Possibly what you want is
>
> corr.t <- function(data, ind) cor(data[ind,])[1,2]
>
> nlaw appears to be a single-column matrix: that will not work either.
>
> On Mon, 1 Sep 2008, ctu at bigred.unl.edu wrote:
>
>> Hi R users,
>> I have one simple question but I really don't know why I can't get it work.
>> The data was adopted from Efron's An introduction to the bootstrap book.
>>> nlaw
>>    LSAT  GPA
>> [1,]  576 3.39
>> [2,]  635 3.30
>> [3,]  558 2.81
>> [4,]  578 3.03
>> [5,]  666 3.44
>> [6,]  580 3.07
>> [7,]  555 3.00
>> [8,]  661 3.43
>> [9,]  651 3.36
>> [10,]  605 3.13
>> [11,]  653 3.12
>> [12,]  575 2.74
>> [13,]  545 2.76
>> [14,]  572 2.88
>> [15,]  594 2.96
>>> nlaw<-as.matrix(law[,-1])
>>> corr.t<-function(data){
>> +        return(boot::corr(data))
>> +        }
>>> law.boot<-boot(data=nlaw,statistic=corr.t,R=49)
>> Error in statistic(data, original, ...) : unused argument(s) (1:15)
>>
>> many thanks for the help
>> Chunhao
>>
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