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Blackboard bold characters

I have seen the unit (or identity operator) typeset via


Is this really the best way to get a double-stroke 1? The obvious guess, \mathbb{1}, does not work.

Or is the use of a double-stroke 1 (rather than "Id" or just a simple "1") for this purpose frowned upon?

  • I would highly recommend \usepackage{bbm} and \newcommand\idop{\bbm 1}. Sep 3 '11 at 20:53
  • This can be confusing.
    – Wok
    Dec 4 '12 at 12:38

Try \mathds from the dsfont package:






The resulting output is:

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