I have this little MWE taken and modificated from the documentation from pag. 6/16 of the guide xyguide:

A \ar@<1ex>[dr]^a \\
& B \ar@<1ex>[ul]^b}

enter image description here

My doubts are:

  1. How can I have the two vectors parallel and have the same direction?

enter image description here

  1. What it the significance of the explanation with an example?

enter image description here

  • 2
    Regarding (1) is it a requirement that the arrow is drawn from B? Otherwise just draw it from A and use \ar@<-1ex>[dr]_a. Though, noadays I'd use tikz-cd
    – daleif
    Mar 23 '21 at 12:47
  • @daleif Hi, my English language it is scarce. I want know as to have two parallels tip-arrows or the end in B or in A. Yes of couse, I agree with you but sometimes I like some of old...packages...:-)..and many users create the diagrams with tikz-cd :-)))
    – Sebastiano
    Mar 23 '21 at 12:50
  • @daleif Sometimes I don't understand English, seriously. I give to Caesar what is Caesar's.
    – Sebastiano
    Mar 23 '21 at 13:32

With an xymatrix I recommend a second arrow from A to B, but with a negative shift:

enter image description here

The code would be:

A \ar@<1ex>[dr]^a\ar@<-1ex>[dr]_b \\
& B}

Here are three ways to do this with tikz-cd. All produce the same image:

enter image description here

\begin{tikzcd} % Two arrows from A to B
A\arrow[dr, "a", shift left=1ex]\arrow[dr, "b"', shift right=1ex]\\

\begin{tikzcd} % left arrow from B to A
A\arrow[dr,"a",shift left=1ex]\\
&B\arrow[ul, "b", leftarrow, shift left=1ex]

\begin{tikzcd} % arrow using 'from' key
A\arrow[dr, "a", shift left=1ex]\\
&B\arrow[from=ul, "b"', shift right=1ex]

Note the use of the extra single quote to place the label on the opposite side: "b"'

  • Hi, and thank you very much for your explanation....In this period I like very much xy package...many users (also I use tikz-cd) use for the simple code tikz-cd. +1 and green check mark.
    – Sebastiano
    Mar 23 '21 at 17:36

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.