hi R users I have a data set with the name AA AA<-1:100 Now I want to get a child array from AA every 10 numbers e.g. ab =c(10,20,30,40,50,60,70,80,100) How could I subtract aa from AA? thank you . -- TANG Jie Email: totangjie@gmail.com Tel: 0086-2154896104 Shanghai Typhoon Institute,China [[alternative HTML version deleted]]
Jeff Newmiller
2013-Jan-14 07:54 UTC
[R] hwo to subtract a child array from the big array?
Although I think I understand "every 10 numbers", I am not so sure how
to interpret "subtract aa from AA" for a couple of reasons.
First, to decimate your data:
ab <- AA[(1:10)*10]
As for subtraction, you have not told us what variable aa is. If you meant
variable ab, it has only 10 values while AA has 100 values. If you try to
subtract ab, R will "recycle" values until you get 10 copies of ab.
If you are thinking of set difference, there is a setdiff function, but that
will only work reliably with integer data (which you have here but may not in
general). However, you may find reading the section on indexing in the
Introduction to R document that ships with R to be very useful. In there it
mentions the effect of using negative index values:
AA[-(1:10)*10]
giving you "the rest of the data".
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Jie Tang <totangjie at gmail.com> wrote:
>hi R users
> I have a data set with the name AA
>AA<-1:100
>Now I want to get a child array from AA every 10 numbers
>e.g.
>ab =c(10,20,30,40,50,60,70,80,100)
>
>How could I subtract aa from AA?
>thank you .