[Xy-pic] Shifting arrow heads

[Ross Moore]

Hello Hamish,

On 20/01/2010, at 12:53 AM, Hamish Ivey-Law wrote:

> Dear xy-pic list,
>
> I am trying to typeset a diagram which has two entries.  There is a
> large entry which is above a small entry, and I would like to have
> multiple arrows from the small entry underneath to different parts of
> the large entry above.  For example, I might have:
>
>   \xymatrix{
>     {A \times B \times C} \\
>     {X} \ar[u] \ar[u]
>   }
>
> and I would like the first \ar[u] to point towards  A  and the second
> to point towards  C.

Just add vector displacements to the [u] targets:

\xymatrix{
     {A\times B \times C}\\
     {X} \ar[u]-<20pt,5pt> \ar[u] \ar[u]+<20pt,-5pt>
   }

If you don't want to guess at the absolute lengths,
then use the extents of the target object itself,
e.g.

\xymatrix{
     {A\times B \times C}\\
     {X} \ar[u]!L(.9) \ar[u] \ar[u]!R(.5)
   }

The attached image shows the result from each of these.
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> Of course, I'd rather avoid splitting the large
> entry into multiple entries as that tends to wreak havoc with the
> typesetting, so I'm looking for a way to shift the head of the \ar[u]
> to the left or right so that it points to the right bit.
>
> Please forgive me if this is a simple question.  I read enough of the
> reference manual to suspect that the answer involves the use of the
> vector objects, but try as I might I couldn't get their syntax
> correct.
>
> Thanks in advance,
> Hamish.


Hope this helps,

	Ross

------------------------------------------------------------------------
Ross Moore                                       ross at maths.mq.edu.au
Mathematics Department                           office: E7A-419
Macquarie University                             tel: +61 (0)2 9850 8955
Sydney, Australia  2109                          fax: +61 (0)2 9850 8114
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