Hi Jonathan,
grep() returns a vector giving either the indices of the elements of
'x' that yielded a match or, if 'value' is 'TRUE', the matched elements
of 'x' (quoting from the help page, see ?grep).
So you probably want to test whether this vector is empty or not - in
other words, whether it has length zero or not:
if( length(grep("hi", "hop", fixed = TRUE)) > 0 )
print('yes, your substring is in your string') else
print('no, your substring is not in your string')
(And you can remove the "fixed = TRUE" if you are only interested in
whether the expression matches or not.)
One off-topic point: you want your "else" at the end of the second line,
not the beginning of the third. R evaluates line by line, and when it
gets to the end of the second line and doesn't see your "else", it has
no way of knowing that the "if" is not yet finished. I've found that
liberal use of curly braces makes life much easier.
HTH,
Stephan
Jonathan schrieb:
Hi,
A noobie question: I'm simply trying to run a conditional statement that
evaluates if a substring is found within a larger string. I find that if it
IS found, my function returns TRUE (great!), but if not, the condition does
not evaluate to FALSE.
ex):
if( grep("hi", "hop", fixed = TRUE) )
print('yes, your substring is in your string')
else print('no, your substring is not in your string')
alternatively, I could replace grep with pmatch:
if (pmatch('hi','hop'))
print('yes, your substring is in your string')
else print('no, your substring is not in your string')
The first example, using grep, returns logical(0). The second, using
pmatch, returns NA. Any idea how to convert either of those to FALSE, or
else a different function that would do the trick?
Thanks,
Jon
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