[18857] in s-news-athena
[S] Mapping a character string into an object
daemon@ATHENA.MIT.EDU (fan@katan.cybercom.net)
Wed Aug 4 16:58:01 1999
From: fan@katan.cybercom.net
Date: Wed, 4 Aug 1999 16:48:43 -0400
Message-Id: <199908042048.QAA03405@katan.cybercom.net>
To: s-news@wubios.wustl.edu
I am working on producing a table of N rows. Each row contains
summaries for a different name, say "A", "B", ...
For each name, there are multiple data vectors corresponding to it.
Then, I apply some operations for these names, one at a time.
I am considering using a loop, so that codes can be
reused. In an attempt, I made a list:
namelist <- c("A", "B", ...)
The job I am thinking about has a diagram as:
for (i in 1:length(namelist))
{
# call the variable named "namelist[i]" for computation.
# this requires "a map from a string to an object"
# An example is:
# cat(a <- mean(*.c),"\t", b<-var(*.d), where * is the ith element of
# namelist.
}
I don't know of a way to refer to different objects from within a loop
as iterator i changes. Please send in your ideas.
The reasons that I didn't combine all the data vectors into a big matrix/array
and then refer it via index are:
1.duplicating data is consuming, especially when the dataset is large.
2.multiple data-vectors for a certain name (e.g., A.c, A.d, A.e) may
not have the same length.
3.length(namelist) could be large.
Let me know if I haven't described the problem well.
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