# [R] Fw: Help with loops(corrected question)

Uwe Ligges ligges at statistik.tu-dortmund.de
Sat May 16 17:07:47 CEST 2009

```
Amit Patel wrote:
>
>
> --- On Fri, 15/5/09, Amit Patel <amitrhelp at yahoo.co.uk> wrote:
>
>> From: Amit Patel <amitrhelp at yahoo.co.uk>
>> Subject: Help with loops
>> To: r-help at r-project.org
>> Date: Friday, 15 May, 2009, 12:17 PM
>> Hi
>> I am trying to create a loop which averages replicates in
>> my data.
>> The original data has many rows. and consists of 40 column
>> zz[,2:41] plus row headings in zz[,1]
>> I am trying to average each set of values (i.e. zz[1,2:3]
>> averaged and placed in average_value[1,2] and so on.
>> below is my script but it seems to be stuck in an endless
>> loop
>> Any suggestions??

If you want row-wise means, rowMeans does it without any loop, but
instead you could loop over the column indices or go without any
explicit loop as in:

averaged_value <- zz[,1:21]
temp <- as.matrix(zz[,2:41])
dim(temp) <- c(nrow(temp),2,20)
# and then either:
temp <- aperm(temp, c(1,3,2))
averaged_value[,2:21] <- rowMeans(temp, dim=2)
#
averaged_value[,2:21] <- apply(temp, c(1,3), mean)

Uwe Ligges

>> for (i in 1:length(zz[,1])) {
>
>> #calculates Meanss
>> #Sample A
>> average_value[i,2] <- rowMeans(zz[i,2:3])
>> average_value[i,3] <- rowMeans(zz[i,4:5])
>> average_value[i,4] <- rowMeans(zz[i,6:7])
>> average_value[i,5] <- rowMeans(zz[i,8:9])
>> average_value[i,6] <- rowMeans(zz[i,10:11])
>>
>> #Sample B
>> average_value[i,7] <- rowMeans(zz[i,12:13])
>> average_value[i,8] <- rowMeans(zz[i,14:15])
>> average_value[i,9] <- rowMeans(zz[i,16:17])
>> average_value[i,10] <- rowMeans(zz[i,18:19])
>> average_value[i,11] <- rowMeans(zz[i,20:21])
>>
>> #Sample C
>> average_value[i,12] <- rowMeans(zz[i,22:23])
>> average_value[i,13] <- rowMeans(zz[i,24:25])
>> average_value[i,14] <- rowMeans(zz[i,26:27])
>> average_value[i,15] <- rowMeans(zz[i,28:29])
>> average_value[i,16] <- rowMeans(zz[i,30:31])
>>
>> #Sample D
>> average_value[i,17] <- rowMeans(zz[i,32:33])
>> average_value[i,18] <- rowMeans(zz[i,34:35])
>> average_value[i,19] <- rowMeans(zz[i,36:37])
>> average_value[i,20] <- rowMeans(zz[i,38:39])
>> average_value[i,21] <- rowMeans(zz[i,40:41])
>>   }
>>
>>
>> thanks
>>
>>
>>
>>
>
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