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Is there any way to 'phantom' text within the align environment?

I have the following code:

a & = b \\
& = c

Apparently, if there a tab alignment character in the argument of the phantom command, compilation will stop. I was trying to make the text within the align environment appear as blank text. Curiously, if I have a cases environment with the tab alignment character inside it, phantom will work when it surrounds the cases environment.


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you could \phantom each individual 'cell' –  cmhughes Aug 27 '12 at 1:20
you could pack the alignment in a minipage with the \phantom wrapped around that, but unfortunately it would foul up the vertical spacing. –  barbara beeton Aug 27 '12 at 12:57

2 Answers 2

up vote 9 down vote accepted

If you "hide" the tab alignment & from align, it will fail to work as expected. This is only because & is read as part of the argument to \phantom, which knowns nothing about & and its use. As such, you either have to spread the \phantom across the aligned components, or use an altogether different approach:

enter image description here

  a & = b + c \\
  \phantom{a} & \phantom{{} = b} + c \\ % Hides some components of above line
    & = d + e \\
    & \phantom{{}= d} + e % Hides some components of above line

In the above example, some components were left untouched to indicate how some spacing correction is sometimes required when using \phantom (for example, when hiding the relation =).

The reason why \phantom around an entire cases structure works is because the tab alignment character is buried within the environment where it makes sense.

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It's probably easier to use textcolor with white:


You need the color package.

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Unusual approach, however I don't consider it good in this case. There are two reasons: (1) unnecessary usage of colours, (2) the hidden text is still copy-pastable, which might be an issue, especially if it's hidden to achieve correct spacing, because then the text does not belong to the output but still would get copied. –  yo' Aug 27 '12 at 6:18

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