[R] apply

[Steven Yen]

On 10/4/2024 5:13 PM, Steven Yen wrote:

> Pardon me!!!
>
> What makes you think this is a homework question? You are not 
> obligated to respond if the question is not intelligent enough for you.
>
> I did the following: two ways to calculate a covariance matrix but 
> wonder how I might replicate the results with "apply". I am not too 
> comfortable with the online documentation of "apply".
>
> > set.seed(122345671) > n<-3 > x<-rnorm(n); x [1] 0.92098449 0.80940115 
> 0.60374785 > cov1<-outer(x-mean(x),x-mean(x))/(n-1); cov1 [,1] [,2] 
> [,3] [1,] 0.0102159207 0.00224105983 -0.0124569805 [2,] 0.0022410598 
> 0.00049161983 -0.0027326797 [3,] -0.0124569805 -0.00273267965 
> 0.0151896601 > cov2<-(x-mean(x))%*%t((x-mean(x)))/(n-1); cov2 [,1] 
> [,2] [,3] [1,] 0.0102159207 0.00224105983 -0.0124569805 [2,] 
> 0.0022410598 0.00049161983 -0.0027326797 [3,] -0.0124569805 
> -0.00273267965 0.0151896601 >
> On 10/4/2024 4:57 PM, Uwe Ligges wrote:
>> Homework questions are not answered on this list.
>>
>> Best,
>> Uwe Ligges
>>
>>
>>
>> On 04.10.2024 10:32, Steven Yen wrote:
>>> The following line calculates standard deviations of a column vector:
>>>
>>> se<-apply(dd,1,sd)
>>>
>>> How can I calculate the covariance matrix using apply? Thanks.
>>>
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