One way is :
dataset = data.table(ssfamed)
dataset[,< whatever "some functions" are on Asfc, Smc, epLsar, etc>,
by="SPECSHOR,BONE"]
Your SPECSHOR and BONE names will be in your result alongside the results of
the<whatever ...>
Or try package plyr which does this sort of thing too. And sqldf may be
better if you know SQL and prefer it. There are actually zillions of ways
to do it : by(), doBy() etc etc
If you get your code working the way its constructed currently, its going
to be very slow, because of those "==". data.table doesn't do that and is
pretty fast for this kind of thing. You might find that plyr is easier to
use and more flexible though if speed isn't an issue, depending on exactly
what you want to do.
Whichever way you decide, consider voting on crantastic for the package you
end up using, and that may be a quick and easy way for you to help new R
users in the future, and help us all by reducing the r-help traffic on the
same subject over and over again.
Note that plyr is the 2nd spot on crantastic, it would have solved your
problem without needing to write that code. If you check crantastic first
and make sure you're aware of popular packages, it might avoid getting stuck
in this way again. It only works if users contribute to it though.
"Ivan Calandra"<ivan.calandra at uni-hamburg.de> wrote in message
news:4B587CDD.4070209 at uni-hamburg.de...
Hi everybody!
To use some functions, I have to transform my dataset into a list, where
each element contains one group, and I have to prepare a list for each
variable I have (altogether I have 15 variables, and many entries per
factor level)
Here is some part of my dataset:
SPECSHOR BONE Asfc Smc epLsar
cotau tx 454.390369 29.261638 0.001136
cotau tx 117.445711 4.291884 0.00056
cotau tx 381.024682 15.313017 0.002324
cotau tx 159.081789 18.134533 0.000462
cotau tm 160.641503 6.411332 0.000571
cotau tm 79.238023 3.828254 0.001182
cotau tm 143.20655 11.921899 0.000192
cotau tm 115.476996 33.116386 0.000417
cotau tm 594.256234 72.538131 0.000477
eqgre tx 188.261324 8.279096 0.000777
eqgre tx 152.444216 2.596325 0.001022
eqgre tx 256.601507 8.279096 0.000566
eqgre tx 250.816445 18.134533 0.000535
eqgre tx 272.396711 24.492879 0.000585
eqgre tm 172.63264 4.291884 0.001781
eqgre tm 189.441097 14.425498 0.001347
eqgre tm 170.743788 13.564472 0.000602
eqgre tm 158.960849 10.385299 0.001189
eqgre tm 80.972408 3.828254 0.000644
gicam tx 294.494001 9.656738 0.000524
gicam tx 267.126765 19.128024 0.000647
gicam tx 81.888658 4.782006 0.000492
gicam tx 168.32908 12.729939 0.001097
gicam tx 123.296056 7.007427 0.000659
gicam tm 94.264887 18.134533 0.000752
gicam tm 54.317395 3.828254 0.00038
gicam tm 55.978883 17.167534 0.000141
gicam tm 279.597993 15.313017 0.000398
gicam tm 288.262556 18.134533 0.001043
What I do next is:
----
list_Asfc<- list()
list_Asfc[[1]]<- ssfamed[ssfamed$SPECSHOR=='cotau'&ssfamed$BONE=='tx', 3]
list_Asfc[[2]]<- ssfamed[ssfamed$SPECSHOR=='cotau'&ssfamed$BONE=='tm', 3]
----
And so on for each level of SPECSHOR and BONE
I'm stuck on 2 parts:
- in a loop or something similar, I would like the 1st element of the
list to be filled by the values for the 1st variable with the first
level of my factors (i.e. cotau + tx), and then the 2nd element with the
2nd level (i.e. cotau + tm) and so on. As shown above, I know how to do
it if I enter manually the different levels, but I have no idea which
function I should use so that each combination of factor will be used.
See what I mean?
- I would then like to run it in a loop or something for each variable.
It is by itself not so complicated, but I don't know how to give the
correct name to my list. I want the list containing the data for Asfc to
be named "list_Asfc".
Here is what I tried:
----
seq.num<- c(seq(3,5,1)) #the indexes of the variables
for(i in 1:length(seq.num)) {
k<- seq.num[i]
name.num<- names(ssfamed)[k]
list<- list()
list[[1]]<- ssfamed[ssfamed$SPECSHOR=='cotau'&ssfamed$BONE=='tx', i]
list[[2]]<- ssfamed[ssfamed$SPECSHOR=='cotau'&ssfamed$BONE=='tm', i]
names(list)<- c("cotau_tx", "cotau_tm") #I have more and the 1st
question should help me on that too
}
----
After names(list) I need to insert something like: name_list<- list
But I don't know how to give it the correct name. How do we change the
name of an object? Or am I on the wrong path?
Thank you in advance for your help.
Ivan
PS: if necessary: under Windows XP, R2.10.
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