Even if this is not a homework question, it smells like one. If you read the 
Posting Guide it warns you that homework is off-topic, so when you impose an 
arbitrary constraint like "must use specific unrelated function" we feel like 
you are either cheating or wasting our time, and it is up to you to explain why 
we should follow you down this rabbit hole, keeping in mind that statistics 
theory per-se is also off-topic here. You have yet to explain why you want to 
do this the hard way.

On October 4, 2024 2:13:26 AM PDT, Steven Yen <sye...@gmail.com> 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 do 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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>>> PLEASE do read the posting guide 
>>> https://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
>       [[alternative HTML version deleted]]
>
>______________________________________________
>R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
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>PLEASE do read the posting guide https://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.

-- 
Sent from my phone. Please excuse my brevity.

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