Hello,
 
A nice guy call Jun Shen was helping me out with this, but I require a bit more help. Below is my data set or list called 'test'. I'm trying to calculate the %RSD for each pair of index and keep it in cronological order if you can imagine a 3rd column with 'date' beside index.
 
    Result Index
1   0.2901    17
2   0.2928    17
3   0.2913    18
4   0.2893    18
5   0.3526     9
6   0.3316     9
7   0.3492    10
8   0.3467    10
9   0.3385    11
10  0.3341    11
11  0.3449    12
12  0.3406    12
13  0.3690    13
14  0.3327    13
15  0.3324    14
16  0.3245    14
17  0.3245    15
18  0.3229    15
19  0.3331    16
20  0.3208    16

 
now this bit of programming works for it how ever it puts the mean of my index back into numeric order.
 
aggregate(test[1],test[2],mean)->inter
names(inter)[2]='mean'
merge(test,inter,all=T)->inter2
inter2$RSV=inter2$Result/inter2$mean

Would anyone know away around this so I could keep the data in cronological order?
 
Kind Regards,
Al


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