From 470c79c035c77fdc3707b5f947e93bf3427319cf Mon Sep 17 00:00:00 2001
From: Steve Jordan <85461103+thisisapple@users.noreply.github.com>
Date: Mon, 2 Sep 2024 10:11:52 -0500
Subject: [PATCH] Update mpl.py

I tested a simply supported beam and added a node in the beam. There was only one element before the node was added. I then added a point load at the new node. See my codes below. When a new node is inserted, the original element will be deleted. Two new elements will be defined accordingly. However, the original code still references the original key in the self.system.element_map[1]. But Key 1 has been deleted. A key error will occur. You can test my model here:

---------------------------------
from anastruct import SystemElements
structure = SystemElements(EA=15000, EI=5000, mesh=101)
# define elements
structure.add_element(location=[[0,0],[10,0]])

# define support
structure.add_support_hinged(node_id=1)
structure.add_support_hinged(node_id=2)
structure.insert_node(element_id=1, factor=0.4)

# define loads
structure.q_load(q=-5, element_id=[2,3],direction='element')
structure.point_load(node_id=3, Fx=5, Fy=0)

# structure.validate()
structure.show_structure()

# solve the numerical problem
structure.solve()

structure.show_bending_moment()

structure.show_axial_force()
---
 anastruct/fem/plotter/mpl.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/anastruct/fem/plotter/mpl.py b/anastruct/fem/plotter/mpl.py
index 01e882e..0057f4f 100644
--- a/anastruct/fem/plotter/mpl.py
+++ b/anastruct/fem/plotter/mpl.py
@@ -871,8 +871,8 @@ def axial_force(
         self.plot_structure(
             figsize, 1, scale=scale, offset=offset, gridplot=gridplot, axes_i=axes_i
         )
-        assert self.system.element_map[1].axial_force is not None
-        con = len(self.system.element_map[1].axial_force)
+        assert list(self.system.element_map.values())[0].axial_force is not None
+        con = len(list(self.system.element_map.values())[0].axial_force)
 
         if factor is None:
             max_force = max(
@@ -982,8 +982,8 @@ def bending_moment(
         self.plot_structure(
             figsize, 1, scale=scale, offset=offset, gridplot=gridplot, axes_i=axes_i
         )
-        assert self.system.element_map[1].bending_moment is not None
-        con = len(self.system.element_map[1].bending_moment)
+        assert list(self.system.element_map.values())[0].bending_moment is not None
+        con = len(list(self.system.element_map.values())[0].bending_moment)
         if factor is None:
             # maximum moment determined by comparing the node's moments and the sagging moments.
             max_moment = max(