R regex gsub separate letters and numbers
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I have a string that's mixed letters and numbers:

    "The sample is 22mg"

I'd like to split strings where a number is immediately followed by letter like this:

    "The sample is 22 mg"

I've tried this:

    gsub('[0-9]+[[aA-zZ]]', '[0-9]+ [[aA-zZ]]', 'This is a test 22mg')

but am not getting the desired results.

Any suggestions?

