Hi,
I turn to you, the R Sages, once again for help. You've never let me down!
(1) Please make the following toy files:
x <- read.table(textConnection("var.1 var.2 var.3 var.1000
indv.1 1 5 9 7
indv.210000 2 9 3 8"), header = TRUE)
y <- read.table(textConnection("var.3 var.1000"), header = TRUE)
write.csv(x, file = "x.csv")
write.csv(y, file = "y.csv")
(2) Pretend you are starting with the files "x.csv" and "y.csv." They come from
another source -- an online database. Pretend that these files are much, much,
much larger. Specifically:
(a) Pretend that "x.csv" contains 1000 columns by 210,000 rows.
(b) "y.csv" contains just header titles. Pretend that there are 90 header
titles in "y.csv" in total. These header titles are a subset of the header
titles in "x.csv."
(3) What I want to do is scan (or import, or whatever the appropriate word is)
only a subset of the columns from "x.csv" into an R. Specifically, I only want
to scan the columns of data from "x.csv" into R that are indicated in the file
"y.csv." I still want to scan in all 210000 rows from "x.csv," but only for the
aforementioned columns listed in "y.csv."
Can you guys recommend a strategy for me? I think I need to use the scan
command, based on the hugeness of "x.csv," but I don't know what exactly to do.
Specific code that gets the job done would be the most useful.
Thank you very much in advance!
Josh
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