What are the conventions regarding notation for variables denoting vectors?

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As you have noted, forcing Greek letters to be "non-italicized" is not very standard (if you want to use it anyway, see Bernard's comment below).

I'd do one of three things:

  1. Bold: $\pmb{\beta}$
  2. Overlined: $\overline{\beta}$
  3. With an arrow: $\vec{\beta}$

To me, the bold option (no. 1) reminds me more of matrix notation, so I'd personally use either 2. or 3.

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joelostblom
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Updated on August 01, 2022

Comments

  • joelostblom
    joelostblom over 1 year

    Should a variable denoting a vector always be in upright font, even when it is a Greek letter?

    When denoting vector variables, I have noticed that it is common to use a bold, non-italic, lowercase character, such as a, b, etc. I use latex for the few equations I write and I have noticed that it is quite cumbersome to create non-italicized lowercase Greek letters. This makes me wonder if Greek letter variables always should be italicized and it would be wrong to force an upright Greek letter for a vector variable.

    What is the preferred way of typesetting a vector variable when it is represented by a Greek character? Should it be in italics and bold, or upright and bold?


    Update

    enter image description here

    Examples, from left to right: upright, bold+upright, italic, italic+bold. The upright letters are using a slightly different font in this example.

    • Bobson Dugnutt
      Bobson Dugnutt about 7 years
      I'm not sure I understand; do you think of for instance $\beta$ as being italicized? How would you make it non-italicized?
    • lulu
      lulu about 7 years
      Not sure if there is a standard. For what it's worth, unless the context makes it clear what everything is, I like to include the arrow as in $\vec v$
    • joelostblom
      joelostblom about 7 years
      @Lovsovs I added an image to better illustrate my question.
    • joelostblom
      joelostblom about 7 years
      @lulu I noticed that representation, but I kind of like the bold-fonted version better. Although, since latex seems to have problems with both upright Greek letters and bolded math, I might just move back to the arrow representation, thanks for reminding me.
    • Marra
      Marra about 7 years
      I agree with @lulu ; whenever it's not clear by the context that a variable is a vector, I put a small arrow above it.
    • Ant
      Ant about 7 years
      I am not a fan of the notation $\vec v$; it's rather cumbersome after a while
    • TZakrevskiy
      TZakrevskiy about 7 years
      The notation conventions vary from field to field and from country to country, so it is hard to imagine a definitive answer. I'd say that the best practice would be to take a look at other publications in your domain and try to write your articles in a manner that the vector nature of your variables can be easily guessed from context.
    • smcc
      smcc about 7 years
      In economics (and I suppose many other fields) it is quite common not to use any special notation to distinguish vectors from scalars, e.g. just write $\beta=(\beta_1,\ldots, \beta_n)$. This seems neater to me, and leaves overlines etc free for other uses.
    • Bernard
      Bernard about 7 years
      In France, Greek letters are traditionally upright.
    • joelostblom
      joelostblom about 7 years
      @smcc Thanks, that's the solution I went with in the end. It also avoids any ambiguity when for example transposing a variable with a line or arrow above it.
  • Bernard
    Bernard about 7 years
    It exists in quite a few font package, and is often known as frenchmath. To mention a few ones: fourier, kpfonts, Minion Pro, mathdesign, newpx or newtx.
  • Bobson Dugnutt
    Bobson Dugnutt about 7 years
    @Bernard Thanks, great to know!
  • joelostblom
    joelostblom about 7 years
    Thanks, in the end I went with the same notation as for any other variable, an italic beta with normal font weight and no added arrows or lines, $\beta$. The other solutions sometimes looked a bit cramped or unclear, such as when transposing the matrix, $\vec{\beta}^T$. It is possible that I can get around that playing with the space between characters, but I don't want to spend too much time optimizing that.
  • Bobson Dugnutt
    Bobson Dugnutt about 7 years
    @cheflo Probably a good decision. Note that you could also use $\underline{\beta}$ for vectors and $\underline{\underline{\beta}}$ for matrices. $\underline{\underline{\beta}}^T$ looks pretty nice IMO.