Always start with the help page. But, the best way to get help on this list is to construct some toy data. Even if imperfect, people will work to help you. Maybe show us some of your actual data.
Of course, if a and b1 are really scalars, I donâ€™t think there is such a thing as the covariance between two scalars
From: huang jialin [mailto:huangpsych@gmail.com]
Sent: Monday, March 12, 2012 11:53 AM
To: Doran, Harold
Cc: r-help@r-project.org
Subject: Re: [R] how to calculate a variance and covariance matrix for a vector
Hi,
Thanks for your response.
I tried to use cov() before, but got NA all over the place.
a and b1 are scalars in the example. So that is the problem. I will start over from the formula.
Thanks again.
Sincerely,
Jialin Huang
On Mon, Mar 12, 2012 at 10:47 AM, Doran, Harold > wrote:
Can you provide sample data? This suggests that a and b1, for example, are scalars. If that is what you actually have then you cannot produce a covariance between two scalars.
> -----Original Message-----
> From: r-help-bounces@r-project.org [mailto:r-help-bounces@r-project.org] On
> Behalf Of huang jialin
> Sent: Monday, March 12, 2012 11:43 AM
> To: r-help@r-project.org
> Subject: [R] how to calculate a variance and covariance matrix for a vector
>
> Hello,
>
> I have a vector {a, b1, b2, b3, b4}. How can I calculate the following
> matrix:
>
> var(a) cov(a, b1) cov(a, b2) cov(a, b3) cov(a, b4)
> cov(a, b1) var(b1) cov(a, b2) cov(a, b3) cov(a, b4)
> ...
> ...
> cov(a, b1) cov(a, b2) cov(a, b3) cov(a, b4) var(b4)
>
> I would very appreciate your inputs. Thank you very much.
>
> Sincerely,
> Jialin Huang
>
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>
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