Re: [R] Create a variable lenght string that can be used in a dimnames statement
Interesting to read all the answers. Personally, I was a bit irked to see
that using a combination of assignments using rownames() and colnames() did
not work as one canceled what the other had done.
But it turns out if we listed to what John really wanted versus what he said
he wanted, then a fairly simple parameterized answer is to add the row and
column names when creating the matrix as in:
# Create a matrix of size M by N rows, initialiazed to NA
# and also add row names that look like row1, row2, ... rowM
# as well as column names that look like col1, col2, ... colN
# Set the parameters and the rest is a one-liner, wrapped a bit
# for legibility:
M <- 2
N <- 4
rowpref <- "row"
colpref <- "col"
myvalues <- matrix(data=NA,
nrow=M,
ncol=N,
dimnames=list(rows=paste("row", seq(M), sep=""),
cols=paste("col", seq(N), sep="")))
The resulting value is:
> myvalues
cols
rows col1 col2 col3 col4
row1 NA NA NA NA
row2 NA NA NA NA
-Original Message-
From: R-help On Behalf Of Sorkin, John
Sent: Tuesday, July 4, 2023 12:17 AM
To: Rolf Turner ; Bert Gunter
Cc: r-help@r-project.org (r-help@r-project.org) ;
Achim Zeileis
Subject: Re: [R] Create a variable lenght string that can be used in a
dimnames statement
My life is complete.
I have inspired a fortune!
John
From: Rolf Turner
Sent: Monday, July 3, 2023 6:34 PM
To: Bert Gunter
Cc: Sorkin, John; r-help@r-project.org (r-help@r-project.org); Achim Zeileis
Subject: Re: [R] Create a variable lenght string that can be used in a
dimnames statement
On Mon, 3 Jul 2023 13:40:41 -0700
Bert Gunter wrote:
> I am not going to try to sort out your confusion, as others have
> already tried and failed.
Fortune nomination!!!
cheers,
Rolf Turner
--
Honorary Research Fellow
Department of Statistics
University of Auckland
Stats. Dep't. (secretaries) phone:
+64-9-373-7599 ext. 89622
Home phone: +64-9-480-4619
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Re: [R] Create a variable lenght string that can be used in a dimnames statement
(Sorry for the double post.)
On Tue, 4 Jul 2023 10:14:43 +0300
Ivan Krylov wrote:
> Try replacing the _second_ paste() in the example above with a c().
What I had forgotten to mention is that you also need to replace the
initial assignment
> string=""
with the following:
string = character()
(NULL and c(), as mentioned by Rui, are also valid options here.)
If you don't do that, the empty string remains an element in the
resulting vector c('', 'xxx1', 'xxx2'), which is not the desired
result. It's awkward to build data structures in an iterative manner,
which is why solutions like Rui's paste0("xxx", 1:2) are considered
more idiomatic.
--
Best regards,
Ivan
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Re: [R] Create a variable lenght string that can be used in a dimnames statement
On Mon, 3 Jul 2023 20:08:06 +
"Sorkin, John" wrote:
> # create variable names xxx1 and xxx2.
> string=""
> for (j in 1:2){
> name <- paste("xxx",j,sep="")
> string <- paste(string,name)
> print(string)
> }
> # Creation of xxx1 and xxx2 works
> string
You need to distinguish between a space separated string and a string
vector. A space separated string is a single object that R won't split
for you unless you tell it to. (Are you coming from a Unix background?
A command line shell will split a space-separated string into a list of
words unless you tell it not to do that, but that's because its main
job is to convert space separated command lines typed by the operator
into lists of command line arguments. R is not like that at all.)
What you're getting here is an individual string. You can confirm that
by typing:
string[1]
and still seeing the whole string. You can also type:
string[2]
and see an NA instead of the second word in the string.
Try replacing the _second_ paste() in the example above with a c().
Given individual strings, paste() concatenates its arguments into
a string. c() concatenates its arguments into a vector of separate
objects. You should still get a variable named `string`, but when you
print it whole, the results will look different (R will separate the
two strings inside that vector), and you should be able to type
string[1] and string[2] and get "xxx1" and "xxx2" respectively.
What about Rui's solution, the one that used paste() and got a vector,
contrary to what I wrote above? Rui gave a vector to paste(). paste()
runs a loop inside it and produces a string for every vector element of
it encounters, unless you tell it to collapse the result.
> zzz <- paste("j","k",string)
Same thing here. paste() adds spaces and returns a string. You need c()
to retain "j" and "k" separate from "xxx1" and "xxx2" as individual
elements of the vector.
It may *look* similar ([1] "j k xxx1 xxx2" vs. [1] "j" "k" "xxx1"
"xxx2"), but the resulting objects are different. When in doubt, use
str() on an object to see its structure.
--
Best regards,
Ivan
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