I would like to improve the following Xy-pic drawing by putting the beginning of the arrow centered under the $x$ and its end centered under $f_u(x) u$:

    E \ar[r]^-{f_u} & \K \ar[r]^-{h_u} & E \\
    x \ar@{|->}[r] \ar@/_1.5pc/[rr]_-{\pi = h_u\circ f_u} & f_u(x) \ar@{|->}[r] & f_u(x)u

I read this answer: Xy-pic moving the position of an arrow but I can't understand how to apply it to my case in the \ar@/_1.5pc/[rr]_-{\pi = h_u\circ f_u} portion of code...

Any idea?


The MWE before tip:


\usepackage{amsmath, amsthm, amssymb}



    E \ar[r]^-{f_u} & \mathbb{K} \ar[r]^-{h_u} & E \\
    x \ar@{|->}[r] \ar@(_,_)[rr]_-{\pi = h_u\circ f_u} & f_u(x) \ar@{|->}[r] & f_u(x)u

  • What's wrong with my "$" (latex)?? – biblio Feb 7 '18 at 19:27
  • Please post complete-but-minimal code rather than a snippet. – Thruston Feb 7 '18 at 20:48
  • We don't have TeX interpretation on this site -- too often we talk about the TeX source rather than the ouput. – Thruston Feb 7 '18 at 20:48

You can do this by changing the arrow bend modifier on the [rr] arrow.

(See p.42 in the reference manual ).

    E \ar[r]^-{f_u} & K \ar[r]^-{h_u} & E \\
    x \ar@{|->}[r] \ar@(_,_)[rr]_-{\pi = h_u\circ f_u} & f_u(x) \ar@{|->}[r] & f_u(x)u

I'm not sure it looks any better though:

enter image description here

If you call \usepackage[all,cmtip]{xy}, the diagram becomes

enter image description here

  • Without the cmtip option, tips on bent arrows are awful; slightly less so on straight arrows. – egreg Feb 8 '18 at 8:28
  • OK, thanks, it's almost perfect, except that the bend is to large (I chose 1.5pc after several tries... ;)). How can I mix the bending control and this modifier, if possible? Otherwise, how can I change the bend with only the modifier? – biblio Feb 8 '18 at 14:19
  • @egreg: how can I call this option? Where do I have to put it (e.g. to which package is it related?) ? – biblio Feb 8 '18 at 14:20
  • @biblio \usepackage[all,cmtip]{xy} – egreg Feb 8 '18 at 14:20
  • OK, but I don't see any difference (what? it's not magical??), so I guess there are commands to add somewhere...? – biblio Feb 8 '18 at 14:22

An alternative with tikz-cd:



\begin{tikzcd}[row sep=6pt]
E \arrow[r,"f_u"] & K \arrow[r,"h_u"] & E \\
x \arrow[r,mapsto]
  \arrow[rr,swap,out=-45,in=-135,"\pi = h_u\circ f_u"] &
  f_u(x) \arrow[r,mapsto] & f_u(x)u


enter image description here

  • Thnks but it doesn't answer my question which is: how to put start and end of arrow centered under the scalar and its image? If I change the angles, the start and end move closer and it's quite the same my first try without the (,) modifier... Or maybe I was wrong somewhere? – biblio Feb 8 '18 at 15:08
  • By the way, I can't see the image, I have a "enter image description here", and when I click on the link, the server answers "unreachable"... Any explanation? – biblio Feb 8 '18 at 15:10
  • @biblio Apparently you can't momentarily reach Imgur, try again later. – egreg Feb 8 '18 at 15:16
  • OK, it seems it depends on the computer... – biblio Feb 9 '18 at 19:26

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