# Formatting of coordinates?

In case I want to describe the pixels of a picture with cartesian coordinates, how would I properly typeset the coordinates? Is p_\mathrm{x}, p_\mathrm{y} correct or rather c_x, c_y? x and y represent the global cartesian coordinates -- again: italic or not?

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Related Question: Typesetting coordinates. –  Peter Grill Jun 11 '12 at 22:38
I think this is a matter of style, but I think the x and y should be italic (as in $c_x$) as then the association with $x$ is clear. –  Peter Grill Jun 11 '12 at 22:41

I’ll always set them in italic since they are kind of variables. The upright font is used for constant values like Euler’s e etc., functions like the Sine or texts like “min”, “max” which are available as macros (\min and \max)*, “start” or “eff[ective]” In the latter case I recommend to use the \text macro from amsmath (or via mathtools).

* See Count Zero’s comment

Some examples

p_x = 3.5
p_\text{max} = 4
p_{x,\text{max}} = 5
p_\text{min} = \mathrm{e}
p_0 = \sin(\pi)
t_\text{start} = 2\,\mathrm{s}% better use siuntix!
U_\text{eff} = U_0/\sqrt{2}% I recommend to define \newcommand{\eff}{\text{eff}} to use
u_\eff = U_0/\sqrt{2}


Just a thought: I wonder why you need the p? I’d use $x=1$ and $y=2$ or $\vec{p}=(1,2)$ if using p as a vector I’d “access” it’s coordinates–like you did–with p_x and p_y.

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Thank you for your answer. Programatically this is what I actually do. But I am visualizing my approach and there it is necessary to depict a second coordinate system. My thought was to put 'x' and 'y' upright in the indexes, since they serve more as a comment and less as a variable. –  Peter Pablo Jun 12 '12 at 7:17
@PeterPablo: Hm … if they are comments and if this is clearly for the reader I guess it’s possible to set them upright, but I’d prefer the in italic though. In my eyes they are always kinde of variable. I’d even type  the $xy$ coordinate system not the xy coordinate system –  Tobi Jun 12 '12 at 7:35
I think this is more of a nitpicker's comment, but I'd rather use \max, \min, etc. in the indices instead of \text{max}, \text{min}. Typographically it may be the same, but from a markup point of view, I think it's rather different. Hope you don't mind... :) –  Count Zero Jun 12 '12 at 8:08
@CountZero: Thanks. I didn’t know these commands ... –  Tobi Jun 12 '12 at 8:18