[R] How do I multiply labeled vectors of numbers?

[Gabor Grothendieck]

Define nm as the names to be multiplied and then use mapply
on m[-1] and d1[nm] so that the latter's columns are rearranged:

> nm <- names(m)[-1]
> data.frame(m[1], mapply("*", m[-1], d1[nm]))
   class feather jet
1  birds      20  20
2 planes      60  40


On Fri, Dec 12, 2008 at 8:02 PM, Bill McNeill (UW)
<billmcn at u.washington.edu> wrote:
> Thanks for the help.  Data frames are gradually starting to make sense to me.
>
> Here's a related question.  I have two data frames, one looks like this:
>
>> m <- data.frame(class = c("birds", "planes"), feather = c(1,3), jet = c(2,4))
>> m
>   class feather jet
> 1  birds       1   2
> 2 planes     3   4
>
> and the other looks like this
>
>> d1 <- data.frame(jet = c(10), feather = c(20))
>> d1
>   jet feather
> 1   10       20
>
> I want to multiply every value in m by the corresponding value in d1.
> I want to do this for both rows, so that I end up with
>
> class        feather        jet
> 1 birds     1*20 = 20    2*10 = 20
> 2 planes  3*20 = 60    4*10 = 40
>
> As before, the trick is to align numbers by the data frame labels
> "feather", "jet", etc. where those columns may appear in different
> orders in m and d1.  However, it doesn't seem like merge is
> applicable, because here I'm trying to merge on data frame labels
> instead of on values in a column of a data frame.  In any event, I
> haven't been able to figure out how to do it.
>
> On Wed, Dec 10, 2008 at 6:51 PM, Gabor Grothendieck
> <ggrothendieck at gmail.com> wrote:
>>
>> You probably want Marc's solution but just in case note that zoo's merge
>> supports zero fill which means that if you represented the two as zoo
>> objects whose "times" are cat, dog, ...  then we would have:
>>
>>
>> File1 <- "type    n
>> dog        2
>> cat        4
>> horse    6"
>>
>> File2 <- "type    n
>> horse    1
>> dog        3
>> cat        9
>> mouse 11"
>>
>> library(zoo)
>>
>> z1 <- read.zoo(textConnection(File1), header = TRUE, FUN = as.character)
>> z2 <- read.zoo(textConnection(File2), header = TRUE, FUN = as.character)
>>
>> z <- merge(z1, z2, fill = 0)
>> zz <- z[,1] * z[,2]
>>
>> Also note that coredata(zz) and time(zz) extract the data and times
>> respectively.
>>
>>
>> On Wed, Dec 10, 2008 at 6:17 PM, Bill McNeill (UW)
>> <billmcn at u.washington.edu> wrote:
>> > I'm an R newbie trying to do an operation that seems like it should be very
>> > simple, but after much playing around with the interface and reading "An
>> > Introduction to R" I can figure out how to do it.
>> >
>> > I have two text files.  File1 contains:
>> >
>> > type    n
>> > dog        2
>> > cat        4
>> > horse    6
>> >
>> > File2 contains:
>> >
>> > type    n
>> > horse    1
>> > dog        3
>> > cat        9
>> > mouse 11
>> >
>> > I want to read both files into R and multiply corresponding values of n so
>> > that I end up with:
>> >
>> > dog       2*3 = 6
>> > cat        4*9 = 36
>> > horse    6*1 = 6
>> > mouse  0*11 = 0
>> >
>> > Note that the type rows are not necessarily in the same order in the two
>> > files, and that a missing type gets a default n = 0 value.
>> >
>> > I figure the way to do this is use read.table and do the appropriate
>> > manipulation of the factors, but I can't figure out what those manipulations
>> > would be.  Basically I want to use a factor table as a hash table, but I
>> > haven't been able to figure out how to do this, which makes me think I'm not
>> > conceptualizing this is the correct R-ish way.
>> >
>> > Thanks.
>> > --
>> > Bill McNeill
>> > http://staff.washington.edu/billmcn/index.shtml
>> >
>> >        [[alternative HTML version deleted]]
>> >
>> > ______________________________________________
>> > R-help at r-project.org mailing list
>> > https://stat.ethz.ch/mailman/listinfo/r-help
>> > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> > and provide commented, minimal, self-contained, reproducible code.
>> >
>
>
>
> --
> Bill McNeill
> http://staff.washington.edu/billmcn/index.shtml
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>