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Book4_Ch13_Python_Codes/Streamlit_Bk4_Ch13_04.py

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+
+###############
+# Authored by Weisheng Jiang
+# Book 4  |  From Basic Arithmetic to Machine Learning
+# Published and copyrighted by Tsinghua University Press
+# Beijing, China, 2022
+###############
+
+
+import streamlit as st
+import numpy as np
+import plotly.express as px
+import pandas as pd
+
+
+def bmatrix(a):
+    """Returns a LaTeX bmatrix
+
+    :a: numpy array
+    :returns: LaTeX bmatrix as a string
+    """
+    if len(a.shape) > 2:
+        raise ValueError('bmatrix can at most display two dimensions')
+    lines = str(a).replace('[', '').replace(']', '').splitlines()
+    rv = [r'\begin{bmatrix}']
+    rv += ['  ' + ' & '.join(l.split()) + r'\\' for l in lines]
+    rv +=  [r'\end{bmatrix}']
+    return '\n'.join(rv)
+
+with st.sidebar:
+    
+    st.latex(r'''
+             A = \begin{bmatrix}
+    a & b\\
+    c & d
+    \end{bmatrix}''')
+    
+    a = st.slider('a',-2.0, 2.0, step = 0.1, value = 1.0)
+    b = st.slider('b',-2.0, 2.0, step = 0.1, value = 0.0)  
+    c = st.slider('c',-2.0, 2.0, step = 0.1, value = 0.0)  
+    d = st.slider('d',-2.0, 2.0, step = 0.1, value = 1.0) 
+    
+#%%
+
+x1_ = np.linspace(-1, 1, 11)
+x2_ = np.linspace(-1, 1, 11)
+
+xx1,xx2 = np.meshgrid(x1_, x2_)
+
+X = np.column_stack((xx1.flatten(), xx2.flatten()))
+
+# st.write(X)
+A = np.array([[a, b],
+              [c, d]])
+
+X = X@A
+
+# st.write(len(X))
+#%% 
+color_array = np.linspace(0,1,len(X))
+# st.write(color_array)
+X = np.column_stack((X, color_array))
+df = pd.DataFrame(X, columns=['z1','z2', 'color'])
+
+#%% Scatter
+
+st.latex(bmatrix(A))
+
+fig = px.scatter(df, 
+                 x="z1", 
+                 y="z2", 
+                 color='color',
+                 color_continuous_scale = 'rainbow')
+
+fig.update_layout(
+    autosize=False,
+    width=500,
+    height=500)
+
+fig.add_hline(y=0, line_color = 'black')
+fig.add_vline(x=0, line_color = 'black')
+
+fig.update_xaxes(range=[-3, 3])
+fig.update_yaxes(range=[-3, 3])
+fig.update_coloraxes(showscale=False)
+
+st.plotly_chart(fig)
+
+
+