[R] turning comma separated string from multiple choices into flags

[Peter Dalgaard]

June Kim wrote:
> Thank you. The misspelling of Harvard wasn't intended. The data are
> spelled consistently.
>   
OK. One other potential problem: If the strings are substrings of
eachother (as in "Science" and "Statistical Science") then you may need
more care.

And I misremembered: It is probably better to use regexpr(....) != -1
than grep(....) for this purpose because the latter returns indices
rather than a value for each element.

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