[R] Output of tapply function as data frame

[Rui Barradas]

Às 04:30 de 27/03/2024, Ogbos Okike escreveu:
> Warm greetings to you all.
> 
> Using the tapply function below:
> data<-read.table("FD1month",col.names = c("Dates","count"))
> x=data$count
>   f<-factor(data$Dates)
> AB<- tapply(x,f,mean)
> 
> 
> I made a simple calculation. The result, stored in AB, is of the form
> below. But an effort to write AB to a file as a data frame fails. When I
> use the write table, it only produces the count column and strip of the
> first column (date).
> 
> 2005-11-01 2005-12-01 2006-01-01 2006-02-01 2006-03-01 2006-04-01
> 2006-05-01
>   -4.106887  -4.259154  -5.836090  -4.756757  -4.118011  -4.487942
>   -4.430705
> 2006-06-01 2006-07-01 2006-08-01 2006-09-01 2006-10-01 2006-11-01
> 2006-12-01
>   -3.856727  -6.067103  -6.418767  -4.383031  -3.985805  -4.768196
> -10.072579
> 2007-01-01 2007-02-01 2007-03-01 2007-04-01 2007-05-01 2007-06-01
> 2007-07-01
>   -5.342338  -4.653128  -4.325094  -4.525373  -4.574783  -3.915600
>   -4.127980
> 2007-08-01 2007-09-01 2007-10-01 2007-11-01 2007-12-01 2008-01-01
> 2008-02-01
>   -3.952150  -4.033518  -4.532878  -4.522941  -4.485693  -3.922155
>   -4.183578
> 2008-03-01 2008-04-01 2008-05-01 2008-06-01 2008-07-01 2008-08-01
> 2008-09-01
>   -4.336969  -3.813306  -4.296579  -4.575095  -4.036036  -4.727994
>   -4.347428
> 2008-10-01 2008-11-01 2008-12-01
>   -4.029918  -4.260326  -4.454224
> 
> But the normal format I wish to display only appears on the terminal,
> leading me to copy it and paste into a text file. That is, when I enter AB
> on the terminal, it returns a format in the form:
> 
> 008-02-01  -4.183578
> 2008-03-01  -4.336969
> 2008-04-01  -3.813306
> 2008-05-01  -4.296579
> 2008-06-01  -4.575095
> 2008-07-01  -4.036036
> 2008-08-01  -4.727994
> 2008-09-01  -4.347428
> 2008-10-01  -4.029918
> 2008-11-01  -4.260326
> 2008-12-01  -4.454224
> 
> Now, my question: How do I write out two columns displayed by AB on the
> terminal to a file?
> 
> I have tried using AB<-data.frame(AB) but it doesn't work either.
> 
> Many thanks for your time.
> Ogbos
> 
> 	[[alternative HTML version deleted]]
> 
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Hello,

The main trick is to pipe to as.data.frame. But the result will have one 
column only, you must assign the dates from the df's row names.
I also include an aggregate solution.



# create a test data set
set.seed(2024)
data <- data.frame(
   Date = sample(seq(Sys.Date() - 5, Sys.Date(), by = "1 days"), 100L, 
TRUE),
   count = sample(10L, 100L, TRUE)
)

# coerce tapply's result to class "data.frame"
res <- with(data, tapply(count, Date, mean)) |> as.data.frame()
# assign a dates column from the row names
res$Date <- row.names(res)
# cosmetics
names(res)[2:1] <- names(data)
# note that the row names are still tapply's names vector
# and that the columns order is not Date/count. Both are fixed
# after the calculations.
res
#>               count       Date
#> 2024-03-22 5.416667 2024-03-22
#> 2024-03-23 5.500000 2024-03-23
#> 2024-03-24 6.000000 2024-03-24
#> 2024-03-25 4.476190 2024-03-25
#> 2024-03-26 6.538462 2024-03-26
#> 2024-03-27 5.200000 2024-03-27

# fix the columns' order
res <- res[2:1]



# better all in one instruction
aggregate(count ~ Date, data, mean)
#>         Date    count
#> 1 2024-03-22 5.416667
#> 2 2024-03-23 5.500000
#> 3 2024-03-24 6.000000
#> 4 2024-03-25 4.476190
#> 5 2024-03-26 6.538462
#> 6 2024-03-27 5.200000



Also,
I'm glad to help as always but Ogbos, you have been an R-Help 
contributor for quite a while, please post data in dput format. Given 
the problem the output of the following is more than enough.


dput(head(data, 20L))


Hope this helps,

Rui Barradas


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