# How to draw a vertical line of desired length in equations.

I am writing a big formula where a vertical line is needed. Instead of $\vline$ or $|$, does anyone know a way to draw this vertical line of desired length? The formula is something like

$$E\Bigg[ F_{m-1}\Big( \text{some big contents} \Big) |\: \mathcal{F}_1 \Bigg]$$


Thank you very much!

• For lots of examples and techniques for typesetting math, the mathmode documentation is very helpful. It should be part of your TeX distribution. – Alan Munn Jan 2 '11 at 18:53
• Thanks Alan Munn, I guess what you mean is this one: tex.ac.uk/tex-archive/info/math/voss/mathmode/Mathmode.pdf It is very helpful.:-) – Anand Jan 2 '11 at 21:09

Well, if you are manually defining the size, as in the example you could just put a \Bigg| at the right place. Probably better would be using \left, \middle and \right.

By the way: You should prefer $ and $ instead of double .

$E\left[ F_{m-1}\Big( \text{some big contents} \Big) \middle|\: \mathcal{F}_1 \right]$


Try enclosing your expression into \left. and \right\vert, as in

\left.\frac{\partial L}{\partial\bm{\beta}}\right\vert_{\hat\beta}=-2\bm{X'y}+2\bm{X'X\hat\beta}=0


which yields: • Note that there is a dot in \left.. I wondered for a while why it didn't work. – MINATO Azuma Jul 31 '19 at 9:23