[R] Merge and replace data

[Richard O'Keefe]

I'm a little confused, because the sample code does something that
none of the suggestions does.
x1 <- c(116,0,115,137,127,0,0)
x2 <- c(0,159,0,0,0,159,127)

[You] want : xx <- c(116,115,137,127,159, 127)
Assuming that there should have been two copies of 159 in xx, this is
xx <- c(x1[x1 != 0], x2[x2 != 0])
pmax or ifelse would give you
xx <- c(116,159,115,137,127,159,127)  # NOT the desired result

If there really was supposed to be one copy of 159,
you might want to call unique() somewhere.

You really need to set out clearly and unambiguously what
you actually want.


On Wed, 6 Sept 2023 at 01:42, roslinazairimah zakaria <roslinaump using gmail.com>
wrote:

> Thank you for the general code. Really appreciate it.
>
>
> On Tue, Sep 5, 2023 at 7:59 PM Eric Berger <ericjberger using gmail.com> wrote:
>
> > As Duncan points out, ifelse() provides a more general approach than
> > the specific pmax().
> >
> > Even more generally, you might want to consider the apply() function
> > (and its relatives sapply(), lapply(), ...)
> >
> > For example
> >
> > apply(cbind(x1,x2), MAR=1, max)
> >
> > In the above statement, x1 and x2 are combined into two columns, MAR=1
> > says apply the following function to each row,
> > and max specifies the function to be applied. The summary is that this
> > statement applies the max to each row in the object
> > specified by the first argument. It's very general because you can
> > replace max by an arbitrary function.
> >
> > Similarly, if you get more into R you might modify the above using
> > chained operations. The following rewrites the above
> > by piping cbind(x1,x2) into the apply command. Not a necessary feature
> > to know but eventually will assist you in writing code that does
> > not require a lot of intermediate variables.
> >
> > cbind(x1,x2) |> apply(MAR=1,max)
> >
> > On Tue, Sep 5, 2023 at 2:45 PM Duncan Murdoch <murdoch.duncan using gmail.com>
> > wrote:
> > >
> > > On 05/09/2023 4:55 a.m., roslinazairimah zakaria wrote:
> > > > Hi all,
> > > >
> > > > I have these data
> > > >
> > > > x1 <- c(116,0,115,137,127,0,0)
> > > > x2 <- c(0,159,0,0,0,159,127)
> > > >
> > > > I want : xx <- c(116,115,137,127,159, 127)
> > > >
> > > > I would like to merge these data into one column. Whenever the data
> is
> > '0'
> > > > it will be replaced by the value in the column which is non zero..
> > > > I tried append and merge but fail to get what I want.
> > > >
> > >
> > > Others have pointed out pmax(x1, x2).  For the sample data, even x1+x2
> > > would give the same answer.
> > >
> > > The real question is what you want to do if both x1 and x2 have
> non-zero
> > > entries, or negative entries:
> > >
> > >    pmax(x1, x2)
> > >
> > > will pick the larger one.  It might be zero if the other is negative,
> > > and that doesn't match your description.
> > >
> > >    x1+x2
> > >
> > > will just give the sum, which doesn't match your description if both
> are
> > > non-zero.
> > >
> > > But maybe you want the x1 value unless it is zero, even if it is
> smaller
> > > than the x2 value:  then you would use
> > >
> > >    ifelse(x1 != 0, x1, x2)
> > >
> > > Similarly
> > >
> > >    ifelse(x2 != 0, x2, x1)
> > >
> > > would prefer the x2 value.
> > >
> > > You should think about what you would do in these other cases as well.
> > >
> > > Duncan Murdoch
> > >
> > > ______________________________________________
> > > R-help using 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.
> >
>
>
> --
> *Roslinazairimah Zakaria*
> *Tel: +609-5492370; Fax. No.+609-5492766*
>
> *Email: roslinazairimah using ump.edu.my <roslinazairimah using ump.edu.my>;
> roslinaump using gmail.com <roslinaump using gmail.com>*
> Faculty of Industrial Sciences & Technology
> University Malaysia Pahang
> Lebuhraya Tun Razak, 26300 Gambang, Pahang, Malaysia
>
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>
> ______________________________________________
> R-help using 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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