On Nov 14, 2011, at 4:20 AM, Michael Griffiths wrote:
Good morning R list,
My apologies if this has *already* answered elsewhere, but I have
not found
the answer that I am looking for.
I have a character string, i.e.
form<-c('~ A + B + C + C / D + E + E / F + G + H + I + J + K + L * M')
Now, my aim is to find the position of all those instances of '*'
and to
remove said '*'. However, I would also like to remove the preceding
variable name before the '*', the math operator preceding this, and
also
the variable name after the '*'. So, here I would like to remove
'+L*M'
This would be a very narrow implementation that requires the +/spc/
alnum/spc/*/alnum sequence exactly;
> sub("\\+*\\s*[[:alnum:]]*\\s*\\*.[[:alnum:]]*", "", form)
[1] "~ A + B + C + C / D + E + E / F + G + H + I + J + K "
This is a more general implementation using the "*" operator that
matches each of the preceding item 0 or more times.
form<-c('~ A + B + C + C / D + E + E / F + G + H + I + J + K + L * M',
'~ A + B + C + C / D + E + E / F + G + H + I + J + K + L*M',
'~ A + B + C + C / D + E + E / F + G + H + I + J + K +Llll*M'
)
> sub("\\+*\\s*[[:alnum:]]*\\s*\\*.[[:alnum:]]*", "", form)
[1] "~ A + B + C + C / D + E + E / F + G + H + I + J + K "
[2] "~ A + B + C + C / D + E + E / F + G + H + I + J + K "
[3] "~ A + B + C + C / D + E + E / F + G + H + I + J + K "
---stripped out code---
--
David Winsemius, MD
West Hartford, CT
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