[R] Replace NAs in split lists

PIKAL Petr
2018-01-08T10:29:40Z

Hi

With the example, na.locf seems to be the easiest way.
> library(zoo)

> na.locf(df1)
  ID ID_2 Firist Value
1  a   aa   TRUE     2
2  a   ab  FALSE     2
3  a   ac  FALSE     2
4  b   aa   TRUE     5
5  b   ab  FALSE     5

Cheers
Petr

> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Jeff
> Newmiller
> Sent: Monday, January 8, 2018 9:13 AM
> To: r-help at r-project.org; Ek Esawi <esawiek at gmail.com>
> Subject: Re: [R] Replace NAs in split lists
>
> Upon closer examination I see that you are not using the split version of
> df1 as I usually would, so here is a reproducible example:
>
> #----
> df1 <- read.table( text> "ID ID_2 Firist Value
> 1  a   aa   TRUE     2
> 2  a   ab  FALSE    NA
> 3  a   ac  FALSE    NA
> 4  b   aa   TRUE     5
> 5  b   ab  FALSE    NA
> ", header=TRUE, as.is=TRUE )
>
> sdf <- split( df1, df1$ID )
> # note the extra [ 1 ] in case you have more than one non-NA value # per ID
> sdf2 <- lapply( sdf
>                , function( z ) {
>                   z$Value <- ifelse( is.na( z$Value )
>                                    , z$Value[ !is.na( z$Value ) ][ 1 ]
>                                    , z$Value
>                                    )
>                   z
>                  }
>                )
> df2 <- do.call( rbind, sdf2 )
> df2
> #>     ID ID_2 Firist Value
> #> a.1  a   aa   TRUE     2
> #> a.2  a   ab  FALSE     2
> #> a.3  a   ac  FALSE     2
> #> b.4  b   aa   TRUE     5
> #> b.5  b   ab  FALSE     5
>
> # or using tidyverse methods
>
> library(dplyr)
> #>
> #> Attaching package: 'dplyr'
> #> The following objects are masked from 'package:stats':
> #>
> #>     filter, lag
> #> The following objects are masked from 'package:base':
> #>
> #>     intersect, setdiff, setequal, union
> df3 <- (   df1
>         %>% group_by( ID )
>         %>% do({
>                mutate( .
>                      , Value = ifelse( is.na( Value )
>                                      , Value[ !is.na( Value ) ][ 1 ]
>                                      , Value
>                                      )
>                      )
>             })
>         %>% ungroup
>         )
> df3
> #> # A tibble: 5 x 4
> #>   ID    ID_2  Firist Value
> #>   <chr> <chr> <lgl>  <int>
> #> 1 a     aa    T          2
> #> 2 a     ab    F          2
> #> 3 a     ac    F          2
> #> 4 b     aa    T          5
> #> 5 b     ab    F          5
> #----
>
> On Sun, 7 Jan 2018, Jeff Newmiller wrote:
>
> > Why do you want to modify df1?
> >
> > Why not just reassemble the parts as a new data frame and use that
> > going forward in your calculations? That is generally the preferred
> > approach in R so you can re-do your calculations easily if you find a
> > mistake later.
> > --
> > Sent from my phone. Please excuse my brevity.
> >
> > On January 7, 2018 7:35:59 PM PST, Ek Esawi <esawiek at
gmail.com> wrote:
> >> I just came up with a solution right after i posted the question,
but
> >> i figured there must be a better and shorter one.than my solution
> >> sdf1[[1]][1,4]<-lapplyresults[[1]]
> >> sdf1[[2]][1,4]<-lapplyresults[[2]]
> >>
> >> EK
> >>
> >> On Sun, Jan 7, 2018 at 10:13 PM, Ek Esawi <esawiek at
gmail.com> wrote:
> >>> Hi all--
> >>>
> >>> I stumbled on this problem online. I did not like the solution
given
> >>> there which was a long UDF. I thought why cannot split and l/s
apply
> >>> work here. My aim is to split the data frame, use l/sapply,
make
> >>> changes on the split lists and combine the split lists to new
data
> >>> frame with the desired changes/output.
> >>>
> >>> The data frame shown below has a column named ID which has 2
> >> variables
> >>> a and b; i want to replace the NAs on the Value column by 2,
which
> >>> is the only numeric entry, for ID=a and by 5 for ID=b.
> >>>
> >>> I worked out the solution but could not replace the results in
the
> >> split lists.
> >>>
> >>> Original dataframe , df1
> >>>   ID ID_2 Firist Value
> >>> 1  a   aa   TRUE     2
> >>> 2  a   ab  FALSE    NA
> >>> 3  a   ac  FALSE    NA
> >>> 4  b   aa   TRUE     5
> >>> 5  b   ab  FALSE    NA
> >>> Sdf1
> >>> $a
> >>> ID ID_2 Firist Value
> >>> 1  a   aa   TRUE     2
> >>> 2  a   ab  FALSE    NA
> >>> 3  a   ac  FALSE    NA
> >>> $b
> >>>   ID ID_2 Firist Value
> >>> 4  b   aa   TRUE     5
> >>> 5  b   ab  FALSE    NA
> >>> Desired results
> >>> ID ID_2 Firist Value
> >>> 1  a   aa   TRUE    2
> >>> 2  a   ab  FALSE    2
> >>> 3  a   ac  FALSE    2
> >>>
> >>> $b
> >>>   ID ID_2 Firist Value
> >>> 4  b   aa   TRUE     5
> >>> 5  b   ab  FALSE     5
> >>>
> >>> My code
> >>>
> >>> sdf <- split(df1,df$ID)
> >>> lapply(sdf, function(z)
> >> ifelse(is.na(z$Value),z$Value[!is.na(z$Value)],z$Value))
> >>> result:
> >>> $ a: num [1:3] 2 2 2
> >>> $ b: num [1:2] 5 5
> >>>
> >>> How could I put these two lists back in the split data frame,
sdf1?
> >>> Then I could use do.call to reassemble a data frame from the
split
> >>> lists,
> >>>
> >>> Thanks,
> >>> EK
> >>
> >> ______________________________________________
> >> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more,
see
> >> 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.
> >
> > ______________________________________________
> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > 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.
> >
>
> ---------------------------------------------------------------------------
> Jeff Newmiller                        The     .....       .....  Go Live...
> DCN:<jdnewmil at dcn.davis.ca.us>        Basics: ##.#.       ##.#.
Live Go...
>                                        Live:   OO#.. Dead: OO#..  Playing
> Research Engineer (Solar/Batteries            O.O#.       #.O#.  with
> /Software/Embedded Controllers)               .OO#.       .OO#.  rocks...1k
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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.

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