Thank you. It works great.
Kristian
2011/9/16 R. Michael Weylandt <michael.weyla...@gmail.com>
> I think changing nrow() to NROW() will get around that error. However,
> this, as you can see, this goes a little astray at the end. Perhaps
> something like this will work for you:
>
> z.ext <- rbind(z,array(0,c(9,3)))
> z.out <- array(0, c(3,3,9))
>
> for(i in 1:9){
> z.out[,,i] <- cbind(z.ext[c(i,i+3,i+6),])
> }
> print(z.out)
>
> Hope this helps,
>
> Michael Weylandt
>
>
> On Wed, Sep 14, 2011 at 3:42 PM, Kristian Lind <
> kristian.langgaard.l...@gmail.com> wrote:
>
>> Hi,
>>
>> I'm solve a problem where I want to select every 3rd row from a matrix. I
>> do
>> this for all rows in a loop. This gives me "i" matrices with different
>> number of rows
>>
>> I want to stack these matrices in an array and fill the blanks with zero.
>>
>> Does anyone have any suggestions on how to go about this?
>>
>> So i want to go from
>>
>> [,1] [,2] [,3]
>> [1,] 1 1 1
>> [2,] 2 2 2
>> [3,] 3 3 3
>> [4,] 4 4 4
>> [5,] 5 5 5
>> [6,] 6 6 6
>> [7,] 7 7 7
>> [8,] 8 8 8
>> [9,] 9 9 9
>>
>> to
>>
>> , , 1
>>
>> [,1] [,2] [,3]
>> [1,] 1 1 1
>> [2,] 4 4 4
>> [3,] 7 7 7
>>
>> , , 2
>>
>> [,1] [,2] [,3]
>> [1,] 2 2 2
>> [2,] 5 5 5
>> [3,] 8 8 8
>>
>> , , 3
>>
>> [,1] [,2] [,3]
>> [1,] 3 3 3
>> [2,] 6 6 6
>> [3,] 9 9 9
>>
>> , , 4
>>
>> [,1] [,2] [,3]
>> [1,] 4 4 4
>> [2,] 7 7 7
>> [3,] 0 0 0
>>
>> ...
>>
>> , , 9
>>
>> [,1] [,2] [,3]
>> [1,] 9 9 9
>> [2,] 0 0 0
>> [3,] 0 0 0
>>
>>
>> Here's my go at it
>>
>> z <- array(c(1:9), c(9,3))
>> z1 <- array(0, c(3,3,9))
>> for(i in 1:9){
>> if(nrow(z[seq(i,9,3),]) == 2)
>> z1[,,i] <- rbind(z[seq(i,9,3),],c(0,0,0))
>> else
>> z1[,,i] <- z[seq(i,9,3),]
>> }
>> print(z1)
>>
>> I get the following error: Error in if (nrow(z[seq(i, 9, 3), ]) == 2) z1[,
>> ,
>> i] <- rbind(z[seq(i, :
>> argument is of length zero
>>
>> This is because nrow(z[seq(i, 9, 3) becomes NULL.
>> Furthermore, this doesn't take care of the case where nrow(z[seq(i,9,3),])
>> ==1
>>
>> Sorry for the long email and thank you in advance for reading it ;)
>>
>> Kristian
>>
>> [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help@r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
>
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