[R] Antwort: Re: Merging variables

PIKAL Petr petr.pikal at precheza.cz
Tue Jun 7 13:12:22 CEST 2016


Hi

> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of
> G.Maubach at weinwolf.de
> Sent: Tuesday, June 7, 2016 8:19 AM
> To: Michael Dewey <lists at dewey.myzen.co.uk>
> Cc: r-help at r-project.org
> Subject: [R] Antwort: Re: Merging variables
>
> Hi Michael,
>
> yes, I was astonished about this behaviour either. I have worked with SPSS a
> lot - and that works different.

If you want to join two data frames by common names you can use use

merge(dat1, dat2, ....)

without specifing by. From help page:

By default the data frames are merged on the columns with names they both have, but separate specifications of the columns can be given by by.x and by.y. The rows in the two data frames that match on the specified columns are extracted, and joined together.

>
> I would like to share some of my data. Can you tell me how I can dump a
> dataset in a way that I can post it here as text?

copy result of dput directly to your mail

dput(dat)
structure(list(hz = c(0, 25, 50), vykon = c(0, 11.6, 22.6)), .Names = c("hz",
"vykon"), row.names = c(NA, -3L), class = "data.frame")

We can use

dat <- structure(list(hz = c(0, 25, 50), vykon = c(0, 11.6, 22.6)), .Names = c("hz",
"vykon"), row.names = c(NA, -3L), class = "data.frame")

to reconstruct the object.

Regards
Petr

>
> Kind regards
>
> Georg
>
>
>
>
> Von:    Michael Dewey <lists at dewey.myzen.co.uk>
> An:     G.Maubach at weinwolf.de, r-help at r-project.org,
> Datum:  06.06.2016 15:45
> Betreff:        Re: [R] Merging variables
>
>
>
> X-Originating-<%= hostname %>-IP: [217.155.205.190]
>
> Dear Georg
>
> I find it a bit surprising that you end up with customer.x and customer.y. Can
> you share with us a toy example of two data.frames which exhibit this
> behaviour?
>
> On 06/06/2016 13:29, G.Maubach at weinwolf.de wrote:
> > Hi All,
> >
> > I merged two datasets:
> >
> > ds_merge1 <- merge(x = ds_bw_customer_4_match, y =
> > ds_zww_customer_4_match,
> >   by.x = "customer", by.y = "customer",
> >   all.x = TRUE, all.y = FALSE)
> >
> > R created a new dataset with the variables customer.x and customer.y.
> > I would like to merge these two variable back together. I wrote a
> > little function (code can be run) for it:
> >
> > -- cut --
> >
> > customer.x <- c("Miller", "Smith", NA,    "Bird", NA)
> > customer.y <- c("Miller",  NA,     "Doe", "Fish", NA)
> > ds_test <- data.frame(customer.x, customer.y, stringsAsFactors =
> > FALSE)
> >
> > t_merge_variables <-
> >   function(dataset,
> >            var1,
> >            var2,
> >            merged_var) {
> >
> >     # Initialize
> >     dataset[[merged_var]] = rep(NA, nrow(dataset))
> >     dataset[["mismatch"]] = rep(NA, nrow(dataset))
> >
> >     for (i in 1:nrow(dataset)) {
> >
> >       # Check 1: var1 missing, var2 missing
> >       if (is.na(dataset[[i, var1]]) &
> >           is.na(dataset[[i, var2]])) {
> >         dataset[["mismatch"]] <- 1  # var1 & var2 are missing
> >
> >       # Check 2: var1 filled, var2 missing
> >       } else if (!is.na(dataset[[i, var1]]) &
> >                  is.na(dataset[[i, var2]])) {
> >         dataset[[i, merged_var]] <- dataset[[i, var1]]
> >         dataset[["mismatch"]] <- 0
> >
> >       # Check 3: var1 missing, var2 filled
> >       } else if (is.na(dataset[[i, var1]]) &
> >                  !is.na(dataset[i, var2])) {
> >         dataset[[i, merged_var]] <- dataset[[i, var2]]
> >         dataset[["mismatch"]] <-  0
> >
> >       # Check 4: var1 == var2
> >       } else if (dataset[[i, var1]] == dataset[[i, var2]]) {
> >       dataset[[i, merged_var]] <- dataset[[i, var1]]
> >       dataset[["mismatch"]] <- 0
> >
> >       # Leftover: var1 != var2
> >       } else {
> >         dataset[[i, merged_var]] <- NA
> >         dataset[["mismatch"]] <- 2  # var1 != var2
> >       }  # end if
> >     }  # end for
> >     return(dataset)
> > }
> >
> > ds_var_merge1 <- t_merge_variables(dataset = ds_test,
> >   var1 = "customer.x",
> >   var2 = "customer.y",
> >   merged_var = "customer")
> >
> > ds_var_merge1
> >
> > -- cut --
> >
> > It is executed without error but delivers the wrong values in the
> variable
> > "mismatch". This variable is always 1 although it should be NA, 1 or 2
> > respectively.
> >
> > Can you tell me why the variable is not correctly set?
> >
> > Kind regards
> >
> > Georg
> >
> > ______________________________________________
> > 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.
> >
>
> --
> Michael
> http://www.dewey.myzen.co.uk/home.html
>
> ______________________________________________
> 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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