From 8f3a3f952b0e5bd692b9b41d1417c877b0e0425e Mon Sep 17 00:00:00 2001
From: Michael Orlitzky <michael@orlitzky.com>
Date: Sun, 3 Nov 2019 20:57:10 -0500
Subject: [PATCH] mjo-linear_algebra: add the \rank{} of a matrix (or EJA,
 or...).

---
 examples.tex           |  3 ++-
 mjo-linear_algebra.tex | 11 +++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/examples.tex b/examples.tex
index c00279b..dde74d0 100644
--- a/examples.tex
+++ b/examples.tex
@@ -182,7 +182,8 @@
     $L$ is $\adjoint{L}$, or if it's a matrix, then its transpose is
     $\transpose{L}$. Its trace is $\trace{L}$. Another matrix-specific
     concept is the Moore-Penrose pseudoinverse of $L$, denoted by
-    $\pseudoinverse{L}$.
+    $\pseudoinverse{L}$. Finally, the rank of a matrix $L$ is
+    $\rank{L}$.
 
     The span of a set $X$ is $\spanof{X}$, and its codimension is
     $\codim{X}$. The projection of $X$ onto $V$ is $\proj{V}{X}$. The
diff --git a/mjo-linear_algebra.tex b/mjo-linear_algebra.tex
index e2ae9fa..204ad05 100644
--- a/mjo-linear_algebra.tex
+++ b/mjo-linear_algebra.tex
@@ -51,6 +51,17 @@
 % The trace of an operator.
 \newcommand*{\trace}[1]{ \operatorname{trace}\of{{#1}} }
 
+
+% The "rank" of its argument, which is context-dependent. It can mean
+% any or all of,
+%
+%   * the rank of a matrix,
+%   * the rank of a power-associative algebra (particularly an EJA),
+%   * the rank of an element in a Euclidean Jordan algebra.
+%
+\newcommand*{\rank}[1]{ \operatorname{rank}\of{{#1}} }
+
+
 % The ``span of'' operator. The name \span is already taken.
 \newcommand*{\spanof}[1]{ \operatorname{span}\of{{#1}} }
 
-- 
2.43.2