In LyX, what is the most standard way to type a system of equations?

Question

I have a system of equations and would like the alignment to be done on the equal sign.

 phi_{t+1}  =  F\xi_{t}  
 y_t        =  A'X_t
 \theta_t   = \mu + \epsilon_t

What is the most standard way to have this with LyX ? Do I need to install additional packages ?

score 8 · Accepted Answer · 2013-01-08T12:12:32.710

8

Insert → Math → Ams Align Environment

and then in the left part y_t and the right = A'X_t, then hit ctrl-enter to get a new line.

edited Jan 08 '13 at 12:12

answered Jan 08 '13 at 11:15

mins · Answer 2 · 2024-02-02T09:02:21.547

Here is an improved procedure in case you need a system of equations properly aligned on the equal sign, and with a left curly bracket:

It consists in using an AlignedAt environment within separators.

Don't use the Cases environment which provides bracket, multiple rows and columns at once. The alignment would be incorrect for the left column and the spacing would be too large between columns.
Prefer AlignedAt over Align. The former creates columns with no additional space between right/left pairs, contrary to the latter. See Difference between align and alignat environments.

The detailed procedure follows.

Resizing left bracket

Menu Insert | Math | Delimiters, then unselect Keep matched and select a curly bracket for the left delimiter, and None for the right delimiter. Click the Insert button:

Close the dialog. You have got a left bracket and an input box. This box can now be populated by an AlignedAt environment.

Columns

Menu Insert | Math | AMS AlignedAt Environment. This gives you a row of two columns. Enter your first equation.

Rows

Add as many rows as you need using Ctrl-Enter. Be sure the cursor is at the end of the first row, and the status bar displays align AlignedAt and not align. Else you will add rows, but not inside the AlignedAt environment:

2 Answers2