[R] Assigning value of subset argument in "subset" function
David Winsemius
dwinsemius at comcast.net
Mon Aug 24 06:36:42 CEST 2009
On Aug 24, 2009, at 12:24 AM, Steven Kang wrote:
> Hi David,
>
> I have another question regarding the R statement you have provided
> which is:
>
> for (zz in unique(a$xx) ) assign( paste("sub.a", zz, sep="."),
> sum(subset(a, xx==zz)$xxx) )
>
> If the xx variables were characters instead of numerical values, is
> there a way to execute the for loop as above?
I don't understand what the problem is (... no error message or
reproducible code):
> a <- data.frame(x=rep(1:4,2), y=rep(4:7,2), xx=rep(letters[8:11],
2), xxx=rep(12:15,1))
> a
x y xx xxx
1 1 4 h 12
2 2 5 i 13
3 3 6 j 14
4 4 7 k 15
5 1 4 h 12
6 2 5 i 13
7 3 6 j 14
8 4 7 k 15
# the earlier code seems to still "work" without any modification
for (zz in unique(a$xx) ) assign( paste("sub.a", zz, sep="."),
sum(subset(a, xx==zz)$xxx) )
sub.a.h; sub.a.i; sub.a.j; sub.a.k
[1] 24
[1] 26
[1] 28
[1] 30
Was that not what you expected?
--
David.
>
> Thanks.
> On Mon, Aug 24, 2009 at 1:33 PM, David Winsemius <dwinsemius at comcast.net
> > wrote:
>
> On Aug 23, 2009, at 10:51 PM, Steven Kang wrote:
>
>> David, apreciate for your help.
>>
>> However, the result is not what I was expecting.
>>
>> Following on from your code, for example say the input is:
>>
>> a <- data.frame(x=rep(1:4,2), y=rep(4:7,2), xx=rep(8:11,2),
>> xxx=rep(12:15,1))
>>
>> x y xx xxx
>> 1 1 4 8 12
>> 2 2 5 9 13
>> 3 3 6 10 14
>> 4 4 7 11 15
>> 5 1 4 8 12
>> 6 2 5 9 13
>> 7 3 6 10 14
>> 8 4 7 11 15
>>
>> Using the following "subset" function:
>>
>> sub.a <- subset(a, xx == 8)
>>
>> results in:
>>
>> x y xx xxx
>> 1 1 4 8 12
>> 5 1 4 8 12
>>
>> Now, I would like to assign the value of subsetted argument (i.e 8
>> in this case) to be able to use repetitively with other values.
>> For example,
>>
>> sub.a.8 <- sum(sub.a$xxx) to get sum of xxx (=24) satisfying
>> the criteria where xx = 8
>>
>> sub.a.9 <- sum(sub.a$xxx) to get sum of xxx (=26) satisfying
>> the criteria where xx == 9
>> sub.a.10 <- sum(sub.a$xxx) to get sum of xxx (=28) satisfying
>> the criteria where xx == 10 etc
>
> Or perhaps even more programmatically:
>
> > for (zz in unique(a$xx) ) assign( paste("sub.a", zz, sep="."),
> sum(subset(a, xx==zz)$xxx) )
>
>>
>> Please enlighten my problem.
>>
>> thanks
>>
>> On Mon, Aug 24, 2009 at 12:19 PM, David Winsemius <dwinsemius at comcast.net
>> > wrote:
>>
>> On Aug 23, 2009, at 10:12 PM, David Winsemius wrote:
>>
>>
>> On Aug 23, 2009, at 9:56 PM, Steven Kang wrote:
>>
>> Dear R users,
>>
>> I am using "subset" function to filter out specific conditions and
>> would
>> like to use the value of subsetted argument as a name of an object.
>>
>> Specifically, from the following statement:
>>
>> a <- subset(dat, dat$x == "A" & dat$xx == 1 & dat$xxx == "AB" &
>> dat$y
>> == "B" & dat$yy == 2)
>> I would to assign the value of the 3rd subset argument (i.e. "AB")
>> as an
>> object's name such as:
>>
>> a.AB <- sum(a$z)
>>
>> Sounds like you need to read FAQ 7.21:
>>
>> http://cran.r-project.org/doc/FAQ/R-FAQ.html#How-can-I-turn-a-string-into-a-variable_003f
>>
>> Perhaps, ... lightly tested, of course, because no reproducible
>> data provided:
>>
>> assign( paste("a.", sum(a$z), sep=""),
>> subset(dat,x == "A" & xx == 1 & xxx == "AB" & y== "B" & yy
>> == 2) )
>>
>> # you do not need the "dat$"'s in the subset.
>>
>> > a <- data.frame(x=1:4, y=4:7, xx=8:11, xxx=12:15)
>> > a
>> x y xx xxx
>> 1 1 4 8 12
>> 2 2 5 9 13
>> 3 3 6 10 14
>> 4 4 7 11 15
>>
>> Arrgh. Trimmed out the code:
>>
>> assign( paste("a.", sum(a$x), sep=""),
>> subset(a,x == 1 & xx == 8 ) )
>>
>>
>>
>> > a.10
>> x y xx xxx
>> 1 1 4 8 12
>> --
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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