Hi,
Can anyone suggest a clever way to compute a rolling weekly average of the
columns in a matrix? The column bit is straightforward use apply given a
function which does what you want on a column. With regard to a particular
column, the obvious way is to run a for loop indexing the last 7 days and
computing the average . I simply would like to know if there is a better /
quicker way.
Code:
Given a,
> a= array(1:100, dim = c(17,2))
> a
[,1] [,2]
[1,] 1 18
[2,] 2 19
[3,] 3 20
[4,] 4 21
[5,] 5 22
[6,] 6 23
[7,] 7 24
[8,] 8 25
[9,] 9 26
[10,] 10 27
[11,] 11 28
[12,] 12 29
[13,] 13 30
[14,] 14 31
[15,] 15 32
[16,] 16 33
[17,] 17 34
one needs to start computing the average from obs 7 s (at obs 7 you have a
full week to compute the average) and compute the rolling weekly average
from day 7 onwards
Results will look like b
[,1] [,2]
[1,] 4 14
[2,] 5 21
[3,] 6 22
[4,] 7 23
[5,] 8 24
[6,] 9 25
[7,] 10 26
[8,] 11 27
[9,] 12 28
[10,] 13 29
Thanks in advance,
Paolo
On 15 November 2010 20:59, wangwallace <talentt...@gmail.com> wrote:
>
> Hey,
>
> I am hoping someone can help me with a sampling question.
>
> I have a data frame of 8 variables (the first column is the subjects' id):
>
> SubID CSE1 CSE2 CSE3 CSE4 WSE1 WSE2 WSE3 WSE4
> 1 6 5 6 2 6 2 2 4
> 2 6 4 7 2 6 6 2 3
> 3 5 5 5 5 5 5 4 5
> 4 5 4 3 4 4 4 5 2
> 5 5 6 7 5 6 4 4 1
> 6 5 4 3 6 4 3 7 3
> 7 3 6 6 3 6 5 2 1
> 8 3 6 6 3 6 5 4 7
>
> the 6 variables are categorized into two groups with CSE1, CSE2, CSE3, and
> CSE4 in one group and the rest in another group.
>
> >sample(data[,2:4],2,replace=FALSE)
>
> CSE1 CSE2
> 1 6 5
> 2 6 4
> 3 5 5
> 4 5 4
> 5 5 6
> 6 5 4
> 7 3 6
> 8 3 6
>
> Now I want to sample 1 column from another group of variables (i.e., WSE1,
> WSE2, WSE3, WSE4), but I want to restrict a vector I am going to sample
> from
> to only those columns that are not correspond to GROUP 1 variables I have
> sampled. That is, I want to sample a column from WSE3, WSE4 Columns
> corresponding to CSE1 and CSE2 (i.e., WSE1, WSE2) need to be dropped.
>
> How can I do this? what if I want to repeat this whole process (drawing 2
> random columns from CSE1, CSE2, CSE3, and CSE4 first, AND then another
> random column from WSE1, WSE2, WSE3, and WSE4) for 1000 times. any ideas?
>
> Many thanks in advance!!
>
> --
> View this message in context:
> http://r.789695.n4.nabble.com/Sampling-problem-tp3043804p3043804.html
> Sent from the R help mailing list archive at Nabble.com.
>
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