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3.6 Grouping objects

Sometimes you wish to frame or otherwise treat a rectangle of objects as a single object. This is possible with the last two target position forms that we will mention:

t.s merge t with simple s
{t} make t simple

The first will enlarge t to also "cover" the "simple" s (simple means that it cannot have changes etc. attached unless encapsulated in {}s). Here is an example where we merge and frame:

\xymatrix @R=1pc {
 1,1 & 1,2 & 1,3 & 1,4 & 1,5 \\
 2,1 & 2,2 & 2,3 & 2,4 & 2,5
 \save "1,2"."2,4"*[F.]\frm{}
  \ar"1,1" \ar"2,1" \ar"1,5" \ar"2,5"
 \restore }
will typeset


displaymath1118

As you can see, the center of the merged object is the same as the one of the target before the ".."

Finally a more advanced example where we create two merged objects with center in their "real" center, name them and then connect to them. It also shows how macros can be used inside diagrams: they should always expand to "commands" like \ar..., etc.:


displaymath1127

can be typeset by

\def\g#1{\save
 [].[dr]!C="g#1"*[F]\frm{}\restore}%
\xymatrix{
 \g1 A\ar[r]&B\ar[d]&\g2 A'\ar[r]&B'\ar[d]\\
     C\ar[u]&D\ar[l]&    C'\ar[u]&D'\ar[l]
 \ar @{.>}  "g1" ;"1,4"
 \ar @{-->} "2,1";"g2" }
Then we can make arrows from/to the two frames by using the two new targets "g1" and "g2" as shown.

 

Exercise 19.

Change the lambda cube of exercise 12 such it is enclosed in a transparent (i.e., dotted) cube.

Answer.

 

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Kristoffer H. Rose <krisrose@brics.dk> December 19, 1996 / LaTeX2HTMLv96.1-h