# [Xy-pic] xy-pic Digest, Vol 100, Issue 1

peter rejto rejto12 at gmail.com
Sun Aug 25 19:21:27 CEST 2013

PLEASE DELETE.

Thanks
-peter

On 8/25/13, xy-pic-request at tug.org <xy-pic-request at tug.org> wrote:
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> Today's Topics:
>
>    1. Change the orientation of Arrow of xtwocell (Joe Hannon)
>    2. Re: Change the orientation of Arrow of xtwocell
>       (Philip Hirschhorn)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 24 Aug 2013 15:01:21 -0400
> From: Joe Hannon <johannon at gmail.com>
> To: <xy-pic at tug.org>
> Subject: [Xy-pic] Change the orientation of Arrow of xtwocell
> Message-ID: <16338208-EB33-449E-9475-18033F4FF664 at gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> I'm trying to make a diagram similar to this one from wikipedia:
>
> Except that I want to the 2cell double arrow $\eta$ two be pointing from
> node $B$ in the bottom corner toward the middle of arrow $X$ in the top
> row(it is, after all, a natural transformation from $RF$ to $X$), whereas
> the diagram on wikipedia, which I was able to duplicate using the \xtwocell
> command, only wants to make the 2cell point in a direction perpendicular to
> some line chosen by the hop argument of the xtwocell command.
>
> In subsection 3 (Excursions) of section 25.4 (extra options) of chapter 25
> (two-cell) on page 47 of the xyrefer manual
> (http://www.ctex.org/documents/packages/graphics/xyrefer.pdf), it is stated
>
>
>  \xtwocell[?hop?]{?displace?}... connects to the ?pos? displaced by
> ?displace? from the relative cell location specified by ?hop?. The
> displacement can be any string of valid XY-pic commands, but they must be
> enclosed within a group {...}. When the cell location is the target, a null
> grouping {} must be given. When used with the <\omit> nudge, such excursions
> allow a labelled Arrow to be placed anywhere within an XY-pic diagram;
> furthermore the Arrow can be oriented to point in any direction.
>
> So it sounds like it is possible to change the orientation of the arrow
> using the displace argument of the xtwocell command, but I can't figure out
> how to do so. What "string of valid XY-pic commands" can I use to change the
> orientation of the 2cell Arrow, if any?
>
> Here's my example markup
>
> \xymatrix{
> A\ar[d]_F\ar[r]^X\xtwocell[1,0]{}\omit{^<-2>\eta} & C\\
> B\ar@{-->}[ur]_R &
> }
>
> Nothing I tried in the displace argument of \xtwocell[1,0]{} changed the
> arrow in any way.
>
> Alternatively, I tried to use \..compositemap. This oriented the 2cell
> perfectly, but I could not figure out how to put a label at the common
> source/target of the composite arrows.
>
> Any tips would be appreciated.
>
> Regards,
> Joe Hannon
>
>
> ------------------------------
>
> Message: 2
> Date: Sat, 24 Aug 2013 18:24:44 -0400
> From: Philip Hirschhorn <psh at math.mit.edu>
> To: Joe Hannon <johannon at gmail.com>
> Cc: xy-pic at tug.org
> Subject: Re: [Xy-pic] Change the orientation of Arrow of xtwocell
> Message-ID: <alpine.LFD.2.03.1308241820360.12142 at math.mit.edu>
> Content-Type: text/plain; charset="utf-8"; Format="flowed"
>
> If you don't mind ignoring the twocell method and experimenting a bit
> to aim the arrow correctly, you can just insert that double shafted
> arrow by having it point from the lower node to a spot displaced from
> the upper left hand node.  That is:
>
>    \xymatrix{
>      {A} \ar[r]^{X} \ar[d]_{F}
>      & {C}\\
>      {B} \ar@{-->}[ur]_{R}
>      \ar@{=>} [u]+<1.7em,-0.5ex>
>    }
>
> That arrow at the bottom goes from the B to a spot 1.7em to the right
> and 0.5ex below the node above.  It's crude (the 1.7em and -0.5ex were
> found by trial and error), but it might be what you want.
>
> Hope this helps,
> Phil Hirschhorn
>
>
>
>
> On Sat, 24 Aug 2013, Joe Hannon wrote:
>
>> I'm trying to make a diagram similar to this one from wikipedia:
>>
>> Except that I want to the 2cell double arrow $\eta$ two be pointing from
>> node $B$ in the bottom corner toward the middle of arrow $X$ in the top
>> row(it is, after all, a natural transformation from $RF$ to $X$), whereas
>> the diagram on wikipedia, which I was able to duplicate using the
>> \xtwocell command, only wants to make the 2cell point in a direction
>> perpendicular to some line chosen by the hop argument of the xtwocell
>> command.
>>
>> In subsection 3 (Excursions) of section 25.4 (extra options) of chapter 25
>> (two-cell) on page 47 of the xyrefer manual
>> (http://www.ctex.org/documents/packages/graphics/xyrefer.pdf), it is
>> stated
>>
>> \xtwocell[?hop?]{?displace?}... connects to the ?pos? displaced by
>> ?displace? from the relative cell location specified by ?hop?. The
>> displacement can be any string of valid XY-pic commands, but they must be
>> enclosed within a group {...}. When the cell location is the target, a
>> null grouping {} must be given. When used with the <\omit> nudge, such
>> excursions allow a labelled Arrow to be placed anywhere within an XY-pic
>> diagram; furthermore the Arrow can be oriented to point in any direction.
>>
>> So it sounds like it is possible to change the orientation of the arrow
>> using the displace argument of the xtwocell command, but I can't figure
>> out how to do so. What "string of valid XY-pic commands" can I use to
>> change the orientation of the 2cell Arrow, if any?
>>
>> Here's my example markup
>>
>> \xymatrix{
>> A\ar[d]_F\ar[r]^X\xtwocell[1,0]{}\omit{^<-2>\eta} & C\\
>> B\ar@{-->}[ur]_R &
>> }
>>
>> Nothing I tried in the displace argument of \xtwocell[1,0]{} changed the
>> arrow in any way.
>>
>> Alternatively, I tried to use \..compositemap. This oriented the 2cell
>> perfectly, but I could not figure out how to put a label at the common
>> source/target of the composite arrows.
>>
>> Any tips would be appreciated.
>>
>> Regards,
>> Joe Hannon
>> _______________________________________________
>> xy-pic mailing list
>> http://tug.org/mailman/listinfo/xy-pic
>
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> End of xy-pic Digest, Vol 100, Issue 1
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