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I see some tables with a horizontal line placed at the middle of a cell, for terms not available or not applicable. For example, how shall I replace the "N.A." below with such a line?

Auctions of & P\_value &  $\widehat{\theta}$ \\
2  & 0.375 & $\underset{(0.230)}{0.354}$ \\
3  & 0.002 & N.A. \\
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Is \--- enough? Or maybe \-- or even \verb+-+. – Sigur May 16 '14 at 23:33
@Sigur \--- and \--? Did you mean --- and --? – egreg May 17 '14 at 8:09
@egreg, I always had used that. What is the difference? Non breakable? – Sigur May 17 '14 at 15:56
@Sigur \- gives a discretionary hyphen, so \--- is a discretionary hyphen followed by an en-dash. – egreg May 17 '14 at 16:56
@Sigur I don't understand what you're saying; \- is a control symbol, so it's already a complete control sequence name; \--- is three tokens: \-, - and -; unless you change the definition of \-, \- is a discretionary hyphen and, at typesetting time, -- is converted to an en-dash. – egreg May 17 '14 at 17:06
up vote 6 down vote accepted

I suggest defining a command \NA that holds an em-dash ---:

enter image description here


  Auctions of & \detokenize{P_value} &  $\widehat{\theta}$ \\
  2  & 0.375 & $\underset{(0.230)}{0.354}$ \\
  3  & 0.002 & \NA \\


This way, if you don't like it later (in life), just change the definition to something more suitable (perhaps an en-dash --).

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