[R] Antwort: RE: Merging variables

PIKAL Petr petr.pikal at precheza.cz
Tue Jun 7 13:00:29 CEST 2016


Hi

see in line

> -----Original Message-----
> From: G.Maubach at weinwolf.de [mailto:G.Maubach at weinwolf.de]
> Sent: Tuesday, June 7, 2016 8:35 AM
> To: PIKAL Petr <petr.pikal at precheza.cz>
> Cc: Michael Dewey <lists at dewey.myzen.co.uk>; r-help at r-project.org
> Subject: Antwort: RE: [R] Merging variables
>
> Hi Petr,
>
> I would like to describe the data situation in brief:
>
> I have an business warehouse dataset (referred to as BW data) containing
> sales and an ERP  customer master data dataset with additional information
> (referred to as ERP data). Though customer IDs and customer names are
> identical due to the fact that the business warehouse data is derived from
> the ERP data.  Due to selection criteria the BW data contains slightly more
> customers than the ERP data. So customer names and all other information is
> missing in the ERP data for some cases of the BW data.  If I merge those by
> customer ID variable customer names are duplicated using customer.x and
> customer.y as variable names.
>
> As both fields contains the same contents I would have expected R to merge
> this into one variable, e. g. customer. But this is not the case.
>
> Can I adjust the below given merge statement - which looks almost the same
> in my script - that R does the merge of the variables if they are identical
> automatically?
>
> This is my code using left join:
>
> -- cut --
>
> ds_merge1 <- merge(x = ds_bw_customer_4_match, y =
> ds_erp_customer_4_match,
>   by.x = "CustID", by.y = "CustID",
>   all.x = TRUE, all.y = FALSE)


you could use by.x=c("CustId", "customer"), by.y=c("CustId", "customer")

This shall give you merged data both on customer id and customer name.

Regards
Petr

>
> -- cut --
>
> Kind regards
>
> Georg
>
>
>
>
> Von:    PIKAL Petr <petr.pikal at precheza.cz>
> An:     Michael Dewey <lists at dewey.myzen.co.uk>,
> "G.Maubach at weinwolf.de"
> <G.Maubach at weinwolf.de>, "r-help at r-project.org" <r-help at r-
> project.org>,
> Datum:  06.06.2016 17:04
> Betreff:        RE: [R] Merging variables
>
>
>
> Hi Michael
>
> it is simple
>
> set.seed(111)
> let=sample(letters[1:10],6, replace=T)
> dat1<-data.frame(let=let, customer=sample(1:10,6, replace=T))
> let=sample(letters[1:10],6, replace=T)
> dat2<-data.frame(let=let, customer=sample(1:10,6, replace=T))
> merge(dat1, dat2, by.x="let", by.y="let", all=T)
>
> Of course you could add customer variable to by parameter but sometimes it
> is necessary to leave it out. When you have two sets of analytical results
> and you have 2 variables operator but you want to merge those sets e.g. by
> date/hour of analysis.
>
> Regards
> Petr
>
> > -----Original Message-----
> > From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Michael
> > Dewey
> > Sent: Monday, June 6, 2016 3:46 PM
> > To: G.Maubach at weinwolf.de; r-help at r-project.org
> > Subject: 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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