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.boh...@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]]
>
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--
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Office: A 4.23
Email: pd....@cbs.dk Priv: pda...@gmail.com
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