[R] Dynamic reference, right-hand side of function

Bert Gunter
Tue, 05 Dec 2017 01:11:47 -0000

It appears that much of the OP's confusion could be cleared up by studying
relevant resources, e.g. online tutorials or the R Language Maual that
ships with R. This list is not meant to replace such "homework" by
users,
as this lengthy and confusing interchange demonstrates.

Having said that, the OP can check that a matrix of any dimensions is
represented in R as a vector in column major order with a "dim"
attribute.
So:

> a <- matrix(1:10, nr = 5)
> dim(a)
[1] 5 2
> a ## invokes the print() method for matrices
     [,1] [,2]
[1,]    1    6
[2,]    2    7
[3,]    3    8
[4,]    4    9
[5,]    5   10
> is.vector(a)
[1] FALSE
> dim(a) <- NULL ## removes the 'dim' attribute
> is.vector(a)
[1] TRUE
> a
 [1]  1  2  3  4  5  6  7  8  9 10

Cheers,
Bert



Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )

On Mon, Dec 4, 2017 at 4:40 PM, William Dunlap via R-help <
r-help at r-project.org> wrote:

> By the way, R 'vectors' are not the equivalents of mathematical
'vectors'.
> In R, a vector is something that can have arbitrary length and which has
> no 'attributes', other than perhaps element names.  Vectors can be
numeric,
> character,
> complex, lists, etc.   Functions, names, and NULL are not vectors.  In my
> opinion,
> the typical data scientist will rarely find the R vector concept useful and
> it more
> likely to make mistakes with it.
>
> Instead of using as.vector and is.vector, use as.numeric or as.character,
> etc.,
> and is.numeric or is.character, naming the type you want.
>
>
> Bill Dunlap
> TIBCO Software
> wdunlap tibco.com
>
> On Mon, Dec 4, 2017 at 4:23 PM, Love Bohman <love.bohman at
sociology.su.se>
> wrote:
>
> > Hi again!
> > I know you don't find loops evil (well, at least not diabolic :-)
).
> > (After many hours googling I have realized that thinking about loops
> rather
> > than lists is a newbie thing we Stata-users do, I just jokingly
pointed
> it
> > out). Anyway, I'm really happy that you try to teach me some
R-manners.
> > Since I still get questions about what the h**k I mean by my strange
> > question, I sort it out with an example:
> >
> > I had a number of matrices, named in a consecutive manner:
> >
> > aa_2000 <-
as.matrix(read.csv(text="1,0,1,1,0,0,0,0,0,0,1,0,0",
> > header=FALSE))
> > aa_2001 <- as.matrix(read.csv(
text="0,0,0,1,0,1,1,0,0,0,0,1,0,0",
> > header=FALSE))
> > aa_2002 <- as.matrix(read.csv(
text="1,0,0,0,0,0,0,0,1,0,0,0,0,1,0,0",
> > header=FALSE))
> >
> > I needed them to be vectors, and they weren't:
> >
> > is.vector(aa_2000)
> >
> > I finally solved it with this loop (well, I admit I shaped up the last
> > line thanks to William Dunlap):
> >
> > for (year in 2000:2002){
> > varname <- paste0("aa_",year)
> > assign(varname, as.vector(eval(as.name(varname))))
> > }
> >
> > The loop obviously solved the problem:
> >
> > is.vector(aa_2000)
> >
> > However, you have taught me that I should have solved it more elegant
> with
> > a data list:
> >
> > bb_2000 <-
as.matrix(read.csv(text="1,0,1,1,0,0,0,0,0,0,1,0,0",
> > header=FALSE))
> > bb_2001 <- as.matrix(read.csv(
text="0,0,0,1,0,1,1,0,0,0,0,1,0,0",
> > header=FALSE))
> > bb_2002 <- as.matrix(read.csv(
text="1,0,0,0,0,0,0,0,1,0,0,0,0,1,0,0",
> > header=FALSE))
> >
> > is.vector(bb_2000)
> >
> > datanames <- paste0("bb_", 2000:2002)
> > datalist <- lapply(datanames, get)
> > is.vector(datalist[1])
> >
> >
> > I learned a lot of code today, and I really appreciate it! A million
> > thanks!
> > My R-superpowers are, well, not as minuscule as when I woke up this
> > morning.
> >
> > All the best,
> > Love (or maybe LoveR, my future superhero name)
> >
> >
> >
> > -----Ursprungligt meddelande-----
> > Fr?n: Jeff Newmiller [mailto:jdnewmil at dcn.davis.ca.us]
> > Skickat: den 5 december 2017 00:01
> > Till: Love Bohman <love.bohman at sociology.su.se>
> > Kopia: peter dalgaard <pdalgd at gmail.com>; r-help at
r-project.org
> > ?mne: Re: [R] Dynamic reference, right-hand side of function
> >
> > Loops are not evil, and no-one in this thread said they are. But I
> believe
> > your failure to provide a reproducible example is creating confusion,
> since
> > you may be using words that mean one thing to you and something else
to
> the
> > readers here.
> >
> > ################################
> > # A reproducible example includes a tiny set of sample data # Since we
> > cannot reproducibly refer to filenames (your directories # and files
in
> > them are unlikely to be like mine), I will # use a little trick to
read
> > from data in the example:
> >
> > dta <- read.csv( text> > "1.1,3.0,5,7.4,4,2.2,0
> > ", header=FALSE)
> > str(dta)
> > #> 'data.frame':    1 obs. of  7 variables:
> > #>  $ V1: num 1.1
> > #>  $ V2: num 3
> > #>  $ V3: int 5
> > #>  $ V4: num 7.4
> > #>  $ V5: int 4
> > #>  $ V6: num 2.2
> > #>  $ V7: int 0
> >
> > # note that I did not use "data" as the name because # there
is a
> > commonly-used function by that name in R # that could be confused with
> your
> > variable
> >
> > # if you have your object already in memory, you can use the # dput
> > function to create R code that will re-create it in our # working
> > environments.
> >
> > dput( dta )
> > #> structure(list(V1 = 1.1, V2 = 3, V3 = 5L, V4 = 7.4, V5 = 4L,
> > #>     V6 = 2.2, V7 = 0L), .Names = c("V1",
"V2", "V3", "V4", "V5",
> > #> "V6", "V7"), class = "data.frame",
row.names = c(NA, -1L))
> >
> > # which you can put a variable name in front of in your example code:
> >
> > dtasample <- structure(list( V1 = 1.1, V2 = 3, V3 = 5L , V4 = 7.4,
V5 > > 4L, V6 = 2.2, V7 = 0L ) , .Names = c( "V1"
> > , "V2", "V3", "V4", "V5",
"V6", "V7" ), class = "data.frame"
> > , row.names = c(NA, -1L) )
> >
> > # and starting with that line you can make a self-contained #
> > (reproducible) example for us to investigate your problem with
> >
> > # Note that reading a single row of data into R usually gets # a data
> > frame, which looks like a matrix but is not a matrix.
> > # Read the Introduction to R about these two types carefully.
> > # Each column in a data frame can have a different type of data, # but
in
> > a vector or a matrix all rows and columns must be of # the same type.
> >
> > dtam <- as.matrix( dta )
> >
> > # If you have any values that R cannot clearly identify as numeric #
or
> > integer, then the next most general type of variable is # character...
> and
> > that is often something that trips up newbies, # though I have no
> evidence
> > that you have any non-numeric columns # in your data frames.
> >
> > dtax <- as.vector( dta )
> > str(dtax)
> > #> 'data.frame':    1 obs. of  7 variables:
> > #>  $ V1: num 1.1
> > #>  $ V2: num 3
> > #>  $ V3: int 5
> > #>  $ V4: num 7.4
> > #>  $ V5: int 4
> > #>  $ V6: num 2.2
> > #>  $ V7: int 0
> >
> > # This actually makes no change to dta, because a data frame is
already #
> > a list of columns, and lists are just vectors that can hold different
#
> > types of variables, so dta is already a kind of vector.
> >
> > dtan <- as.numeric( dta )
> > str(dtan)
> > #>  num [1:7] 1.1 3 5 7.4 4 2.2 0
> >
> > # I suspect this is what you are trying to accomplish... but really, #
if
> > we had an example of the data you are working with, we would # already
> know.
> > ################################
> >
> > Some more explanations of reproducibility [1][2][3]
> >
> > [1] http://stackoverflow.com/questions/5963269/how-to-make-
> > a-great-r-reproducible-example
> >
> > [2] http://adv-r.had.co.nz/Reproducibility.html
> >
> > [3] https://cran.r-project.org/web/packages/reprex/index.html (read
the
> > vignette)
> >
> >
> > On Mon, 4 Dec 2017, Love Bohman wrote:
> >
> > > :-)
> > > I don't insist on anything, I'm just struggling to learn
a new language
> > and partly a new way of thinking, and I really appreciate the
> corrections.
> > I hope I someday will be able to handle lists in R as easy as I handle
> > loops in Stata...
> > > Thanks again!
> > >
> > > Love
> > >
> > >
> > > -----Ursprungligt meddelande-----
> > > Fr?n: peter dalgaard [mailto:pdalgd at gmail.com]
> > > Skickat: den 4 december 2017 23:09
> > > Till: Love Bohman <love.bohman at sociology.su.se>
> > > Kopia: r-help at r-project.org
> > > ?mne: Re: [R] Dynamic reference, right-hand side of function
> > >
> > > Um, if you insist on doing it that way, at least use
> > >
> > > assign(varname, as.vector(get(varname)))
> > >
> > > -pd
> > >
> > >> On 4 Dec 2017, at 22:46 , Love Bohman <love.bohman at
sociology.su.se>
> > wrote:
> > >>
> > >> Hi!
> > >> Thanks for the replies!
> > >> I understand people more accustomed to R doesn't like
looping much,
> and
> > that thinking about loops is something I do since I worked with Stata
a
> > lot. The syntax from Peter Dalgaard was really clever, and I learned a
> lot
> > from it, even though it didn't solve my problem (I guess it
wasn't very
> > well explained). My problem was basically that I have a data matrix
> > consisting of just 1 row, and I want to convert that row into a
vector.
> > However, when trying to do that dynamically, I couldn't get R to
read the
> > right hand side of the syntax as a variable name instead of a string.
> > However, together with a colleague I finally solved it with the (eval(
> > as.name()) function (I include the loop I used below). I understand
that
> > looping isn't kosher among you more devoted R-users, and
eventually I
> hope
> > I will learn to use lists in the future instead.
> > >>
> > >> Thanks!
> > >> Love
> > >>
> > >>
> > >> for (year in 2000:2007){
> > >> varname <- paste0("aa_",year)
> > >> assign(paste0(varname), as.vector(eval(as.name(varname))))
> > >> }
> > >>
> > >> -----Ursprungligt meddelande-----
> > >> Fr?n: peter dalgaard [mailto:pdalgd at gmail.com]
> > >> Skickat: den 4 december 2017 16:39
> > >> Till: Love Bohman <love.bohman at sociology.su.se>
> > >> Kopia: r-help at r-project.org
> > >> ?mne: Re: [R] Dynamic reference, right-hand side of function
> > >>
> > >> The generic rule is that R is not a macro language, so
looping of
> names
> > of things gets awkward. It is usually easier to use compound objects
like
> > lists and iterate over them. E.g.
> > >>
> > >> datanames <- paste0("aa_", 2000:2007)
> > >> datalist <- lapply(datanames, get)
> > >> names(datalist) <- datanames
> > >> col1 <- lapply(datalist, "[[", 1)
> > >> colnum <- lapply(col1, as.numeric)
> > >>
> > >> (The 2nd line assumes that the damage has already been done
so that
> > >> you have aa_2000 ... aa_2007 in your workspace. You might
> > >> alternatively create the list directly while importing the
data.)
> > >>
> > >> -pd
> > >>
> > >>> On 4 Dec 2017, at 12:33 , Love Bohman <love.bohman at
sociology.su.se>
> > wrote:
> > >>>
> > >>> Hi R-users!
> > >>> Being new to R, and a fairly advanced Stata-user, I guess
part of my
> > problem is that my mindset (and probably my language as well) is
wrong.
> > Anyway, I have what I guess is a rather simple problem, that I now
> without
> > success spent days trying to solve.
> > >>>
> > >>> I have a bunch of datasets imported from Stata that is
labelled
> > aa_2000 aa_2001 aa_2002, etc. Each dataset is imported as a matrix,
and
> > consists of one column only. The columns consists of integer numbers.
I
> > need to convert the data to vectors, which I found several ways to do.
I
> > use, for example:
> > >>> aa_2000 <- as.numeric(aa_2000[,1])
> > >>> However, when trying to automate the task, so I don't
have to write a
> > line of code for each dataset, I get stuck. Since I'm a Stata
user, my
> > first attempt is trying to make a loop in order to loop over all
> datasets.
> > However, I manage to write a loop that works for the left-hand side of
> the
> > syntax, but not for the right-hand side.
> > >>> I have included some examples from my struggles to solve
the issue
> > below, what they all have in common is that I don't manage to call
for
> any
> > "macro" (is that only a Stata-word?) in the right hand side
of the
> > functions. When I try to replace the static reference with a dynamic
one
> > (like in the left-hand side), the syntax just doesn't work.
> > >>>
> > >>> I would very much appreciate some help with this issue!
> > >>> All the best,
> > >>> Love
> > >>>
> > >>> year <- 2002
> > >>> dataname <- paste0("aa_",year)
> > >>> assign(paste0(dataname), as.numeric(aa_2002[,1]))
> > >>>
> > >>> year <- 2003
> > >>> assign(paste0("aa_",year), as.numeric(aa_2003))
> > >>>
> > >>> year <- 2005
> > >>> assign(paste0("aa_",year), aa_2005[,1])
> > >>>
> > >>> list1 <- c(2000:2007)
> > >>> list1[c(7)]
> > >>> assign(paste0("aa_",list1[c(7)]),
as.numeric(paste0(aa_2006)))
> > >>>
> > >>>
> > >>>     [[alternative HTML version deleted]]
> > >>>
> > >>> ______________________________________________
> > >>> 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.
> > >>
> > >> --
> > >> Peter Dalgaard, Professor,
> > >> Center for Statistics, Copenhagen Business School Solbjerg
Plads 3,
> > >> 2000 Frederiksberg, Denmark
> > >> Phone: (+45)38153501
> > >> Office: A 4.23
> > >> Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >
> > > --
> > > Peter Dalgaard, Professor,
> > > Center for Statistics, Copenhagen Business School Solbjerg Plads
3,
> 2000
> > Frederiksberg, Denmark
> > > Phone: (+45)38153501
> > > Office: A 4.23
> > > Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > ______________________________________________
> > > 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.
> >
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> 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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