Hi Laurent,
I am not saying this will work every time and I do recognise that this
is very different from a more general solution that you had envisioned,
but if you are on an UNIX-like system or have the relevant utilities
installed and on the %PATH% on Windows, you can filter the input file
line-by-line using a pipe and an external program:
On Sun, 17 May 2020 15:52:30 +0200
Laurent Rhelp <laurentrh...@free.fr> wrote:
> # sensors to keep
> sensors <- c("N053", "N163")
# filter on the beginning of the line
i <- pipe("grep -E '^(N053|N163)' test.txt")
# or:
# filter on the beginning of the given column
# (use $2 for the second column, etc.)
i <- pipe("awk '($1 ~ \"^(N053|N163)\")' test.txt")
# or:
# since your message is full of Unicode non-breaking spaces, I have to
# bring in heavier machinery to handle those correctly;
# only this solution manages to match full column values
# (here you can also use $F[1] for second column and so on)
i <- pipe("perl -CSD -F'\\s+' -lE \\
'print join qq{\\t}, @F if $F[0] =~ /^(N053|N163)$/' \\
test.txt
")
lines <- read.table(i) # closes i when done
The downside of this approach is having to shell-escape the command
lines, which can become complicated, and choosing between use of regular
expressions and more wordy programs (Unicode whitespace in the input
doesn't help, either).
--
Best regards,
Ivan
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