[R] adding rows as arithmatic calculation on original rows

[Gabor Grothendieck]

Here is a solution using sqldf



library(sqldf)

DF2 <-
structure(list(myID = structure(1:4, .Label = c("a", "b", "c",
"d"), class = "factor"), myType = structure(c(2L, 2L, 1L, 1L), .Label
= c("Double",
"Single"), class = "factor"), myNum1 = c(10, 15, 22, 4), myNum2 = c(11,
25, 33, 6), myNum3 = c(12, 35, 44, 8)), .Names = c("myID", "myType",
"myNum1", "myNum2", "myNum3"), row.names = c(NA, -4L), class = "data.frame")

sqldf("select 1 TotalLevel, '+' myID, myType, avg(myNum1) myNum1,
avg(myNum2) myNum2, avg(myNum3) myNum3
  from DF2
  group by myType
union
  select 0 TotalLevel, *
     from DF2
order by myType, TotalLevel, myID",
method = "raw")[-1]

The output is (display in fixed font):

  myID myType myNum1 myNum2 myNum3
1    c Double   22.0   33.0   44.0
2    d Double    4.0    6.0    8.0
3    + Double   13.0   19.5   26.0
4    a Single   10.0   11.0   12.0
5    b Single   15.0   25.0   35.0
6    + Single   12.5   18.0   23.5



On Fri, Dec 5, 2008 at 3:21 PM, Ferry <fmi.mlist at gmail.com> wrote:
> Dear R users,
>
> Suppose I have the following data.frame:
>
> myID myType myNum1 myNum2 myNum3
> a       Single       10          11           12
> b       Single       15          25           35
> c       Double      22          33           44
> d       Double        4           6             8
>
> and I want to have new records:
>
> myID myType myNum1 myNum2 myNum3
> e      Single       12.5       18           23.5
> f       Double      13          19.5         28
>
> where record e got its myNum1-3 as the average from record a and b, and
> record f got its myNum1-3 as the average from record c and d.
>
> and the final data.frame should be like the following:
>
> myID myType myNum1 myNum2 myNum3
> a       Single       10          11           12
> b       Single       15          25           35
> e       Single       12.5       18           43.5
> c       Double      22          33           44
> d       Double        4           6             8
> f        Double      13          19.5         28
>
> Any idea is appreciated. Thanks beforehand.
>
> Ferry
>
>        [[alternative HTML version deleted]]
>
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