From c7e1e1040d8a29332ab36ab0fdc95591c03584c5 Mon Sep 17 00:00:00 2001
From: Carl Sandrock <carl.sandrock@up.ac.za>
Date: Sun, 24 Feb 2019 17:48:33 +0200
Subject: [PATCH 1/3] Add _repr_latex_ for Jupyter notebooks

---
 control/xferfcn.py | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/control/xferfcn.py b/control/xferfcn.py
index 44a038773..2c298e7b7 100644
--- a/control/xferfcn.py
+++ b/control/xferfcn.py
@@ -268,6 +268,43 @@ def __str__(self, var=None):
     # represent as string, makes display work for IPython
     __repr__ = __str__
 
+    def _repr_latex_(self, var=None):
+        """LaTeX representation of the transfer function, for Jupyter notebook"""
+
+        mimo = self.inputs > 1 or self.outputs > 1
+        if var is None:
+            # ! TODO: replace with standard calls to lti functions
+            var = 's' if self.dt is None or self.dt == 0 else 'z'
+
+        if mimo:
+            outstr = r"$$\begin{bmatrix}"
+        else:
+            outstr = "$$"
+
+        for i in range(self.inputs):
+            for j in range(self.outputs):
+                # Convert the numerator and denominator polynomials to strings.
+                numstr = _tf_polynomial_to_string(self.num[j][i], var=var)
+                denstr = _tf_polynomial_to_string(self.den[j][i], var=var)
+
+
+                outstr += r"\frac{" + numstr + "}{" + denstr + "}"
+                if mimo and j < self.outputs - 1:
+                    outstr += "&"
+            if mimo:
+                outstr += r"\\ "
+
+        if mimo:
+            outstr += r"\end{bmatrix}"
+
+        # See if this is a discrete time system with specific sampling time
+        if not (self.dt is None) and type(self.dt) != bool and self.dt > 0:
+            outstr += "\quad dt = " + self.dt.__str__()
+
+        outstr += "$$"
+
+        return outstr
+
     def __neg__(self):
         """Negate a transfer function."""
 

From e6dccbffc9fd08006d207abbb14af23846e3a183 Mon Sep 17 00:00:00 2001
From: Carl Sandrock <carl.sandrock@up.ac.za>
Date: Mon, 25 Feb 2019 05:18:39 +0200
Subject: [PATCH 2/3] Swap rows and columns in _repr_latex_

---
 control/xferfcn.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/control/xferfcn.py b/control/xferfcn.py
index 2c298e7b7..da615fadb 100644
--- a/control/xferfcn.py
+++ b/control/xferfcn.py
@@ -281,11 +281,11 @@ def _repr_latex_(self, var=None):
         else:
             outstr = "$$"
 
-        for i in range(self.inputs):
-            for j in range(self.outputs):
+        for i in range(self.outputs):
+            for j in range(self.inputs):
                 # Convert the numerator and denominator polynomials to strings.
-                numstr = _tf_polynomial_to_string(self.num[j][i], var=var)
-                denstr = _tf_polynomial_to_string(self.den[j][i], var=var)
+                numstr = _tf_polynomial_to_string(self.num[i][j], var=var)
+                denstr = _tf_polynomial_to_string(self.den[i][j], var=var)
 
 
                 outstr += r"\frac{" + numstr + "}{" + denstr + "}"

From 6cbe0660c95d5d44aaf08ce9bf086ba059d450d1 Mon Sep 17 00:00:00 2001
From: Carl Sandrock <carl.sandrock@up.ac.za>
Date: Thu, 28 Mar 2019 08:10:41 +0200
Subject: [PATCH 3/3] Build list instead of concatenating strings

---
 control/xferfcn.py | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/control/xferfcn.py b/control/xferfcn.py
index da615fadb..1ef0661a5 100644
--- a/control/xferfcn.py
+++ b/control/xferfcn.py
@@ -272,14 +272,15 @@ def _repr_latex_(self, var=None):
         """LaTeX representation of the transfer function, for Jupyter notebook"""
 
         mimo = self.inputs > 1 or self.outputs > 1
+
         if var is None:
             # ! TODO: replace with standard calls to lti functions
             var = 's' if self.dt is None or self.dt == 0 else 'z'
 
+        out = ['$$']
+
         if mimo:
-            outstr = r"$$\begin{bmatrix}"
-        else:
-            outstr = "$$"
+            out.append(r"\begin{bmatrix}")
 
         for i in range(self.outputs):
             for j in range(self.inputs):
@@ -287,23 +288,24 @@ def _repr_latex_(self, var=None):
                 numstr = _tf_polynomial_to_string(self.num[i][j], var=var)
                 denstr = _tf_polynomial_to_string(self.den[i][j], var=var)
 
+                out += [r"\frac{", numstr, "}{", denstr, "}"]
 
-                outstr += r"\frac{" + numstr + "}{" + denstr + "}"
                 if mimo and j < self.outputs - 1:
-                    outstr += "&"
+                    out.append("&")
+
             if mimo:
-                outstr += r"\\ "
+                out.append(r"\\")
 
         if mimo:
-            outstr += r"\end{bmatrix}"
+            out.append(r" \end{bmatrix}")
 
         # See if this is a discrete time system with specific sampling time
         if not (self.dt is None) and type(self.dt) != bool and self.dt > 0:
-            outstr += "\quad dt = " + self.dt.__str__()
+            out += ["\quad dt = ", str(self.dt)]
 
-        outstr += "$$"
+        out.append("$$")
 
-        return outstr
+        return ''.join(out)
 
     def __neg__(self):
         """Negate a transfer function."""