Hello,
It seems you haven't discovered the *apply functions yet. In this case,
since you have a list, the function would be lapply.
1.
Reduce(intersect, lapply(mySplit, function(x) x$product))
2.
lapply(mySplit, function(x) within(x, relative <- diff(c(value[1], value))))
3.
lapply(mySplit, function(x) x[order(x$value), ])
And R-intro.pdf in the doc folder of your installation of R.
Hope this helps,
Rui Barradas
Em 06-06-2012 08:43, bestbird escreveu:
hi,
I met some problems in R, plz help me.
1. How to do a intersect operation among several groups in one list, without
a loop statement? (I think It may be a list)
create data:
myData<- data.frame(product = c(1,2,3,1,2,3,1,2,2),
year=c(2009,2009,2009,2010,2010,2010,2011,2011,2011),value=c(1104,608,606,1504,508,1312,900,1100,800))
mySplit<- split(myData,myData$year)
mySplit
$`2009`
product year value
1 1 2009 1104
2 2 2009 608
3 3 2009 606
$`2010`
product year value
4 1 2010 1504
5 2 2010 508
6 3 2010 1312
$`2011`
product year value
7 1 2011 900
8 2 2011 1100
9 2 2011 800
I want to get intersection of product between every year. I know the
basic is:
intersect(intersect(mySplit[[1]]$product,
mySplit[[2]]$product),mySplit[[3]]$product)
this will give the correct answer:
[1] 1 2
above code lacks reusability, so It should use a for loop:
myIntersect<-mySplit[[1]]$product
for (i in 1:length(mySplit)-1){
myIntersect<-intersect(myIntersect,mySplit[[i+1]]$product)
}
It's correct too, but stll too complex, so my question is:
Can I do the same thing just use another similar intersect function
(without for/repeat/while).
What's this simple function's name ?
2.how to do a relative computation after split (notice: not befor split)?
create data:
myData1<- data.frame(product = c(1,2,3,1,2,3),
year=c(2009,2009,2009,2010,2010,2010),value=c(1104,608,606,1504,508,1312),relative=0)
mySplit1<- split(myData1,myData1$year)
mySplit1
$`2009`
product year value relative
1 1 2009 1104 0
2 2 2009 608 0
3 3 2009 606 0
$`2010`
product year value relative
4 1 2010 1504 0
5 2 2010 508 0
6 3 2010 1312 0
I want compute relative value in the every group, what I mean is , I want
get the result is just like below:
$`2009`
product year value relative
1 1 2009 1104 0
2 2 2009 608 -496
3 3 2009 606 -2
$`2010`
product year value relative
4 1 2010 1504 0
5 2 2010 508 -996
6 3 2010 1312 804
I think to use a loop maybe work, but Is there no direct method on list?
3.how to do a sorting after split, It's just like above question, what I
want is sorting by value:
$`2009`
product year value relative
3 3 2009 606 0
2 2 2009 608 0
1 1 2009 1104 0
$`2010`
product year value relative
5 2 2010 508 0
6 3 2010 1312 0
4 1 2010 1504 0
4. how to do a filtering after split, Yes, It's just like above quetion,
what I want is filtering out data which value is more than 1000:
$`2009`
product year value relative
1 1 2009 1104 0
$`2010`
product year value relative
4 1 2010 1504 0
6 3 2010 1312 0
--
View this message in context:
http://r.789695.n4.nabble.com/problem-about-set-operation-and-computation-after-split-tp4632496.html
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