I need to write a case differentiation in LyX which contains sums but here is the problem.


-\sum_{j\text{=1}}^{N}a_{j}^{(1)} & \text{}\\

gives that

enter image description here

But I want that indices of sum would be over the sum like this:

enter image description here

How to do that?

  • 2
    you could use \displaystyle -\sum.... But note \text{=1} is wrong the =1 should be in math mode not text mode Commented Jan 7, 2016 at 12:22
  • 3
    The package mathtools provides the dcases environment for this.
    – egreg
    Commented Jan 7, 2016 at 12:25

1 Answer 1


In LyX, put the cursor just to the right of sigma (but before the limits). Then either type the shortcut Alt + M, Shift + L, L; or go to Edit > Math > Change Limits Type > Display.

  • This seems to work fine! Thank you @scottkosty
    – zygimantus
    Commented Jan 7, 2016 at 14:03

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