R help - Apr 2006 - VARIANCE across each ROW

I have a very large matrix. I would like to display the variance across each
row.

In other words, I want to output a vector containing the values of variance
across row.

When I use the function var(), it seems to give me the variability of each
column.

Any ideas??

	[[alternative HTML version deleted]]

?apply
apply(data,1,var)
On Sat, 01 Apr 2006 21:27:56 -0500, mark salsburg  
<mark.salsburg at gmail.com> wrote:
> I have a very large matrix. I would like to display the variance across  
> each
> row.
>
> In other words, I want to output a vector containing the values of  
> variance
> across row.
>
> When I use the function var(), it seems to give me the variability of  
> each
> column.
>
> Any ideas??
>
> 	[[alternative HTML version deleted]]
>
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Try this:

# test data
set.seed(1)
x <- matrix(rnorm(24), 6) # 6x4 matrix

sd(t(x))^2 # [1] 0.5631489 1.9047905 0.7813566 0.7415535 0.4992331 1.7095818

# same but generates an intermediate 6x6 matrix
# so less desirable if real matrix has large number of rows

diag(var(t(x))


On 4/1/06, mark salsburg <mark.salsburg at gmail.com>
wrote:
> I have a very large matrix. I would like to display the variance across
each
> row.
>
> In other words, I want to output a vector containing the values of variance
> across row.
>
> When I use the function var(), it seems to give me the variability of each
> column.
>
> Any ideas??