.

bac1/q1/29sept/plot.py

@@ -0,0 +1,75 @@
+#!/usr/bin/env python3
+
+import matplotlib.pyplot as plt
+import numpy as np
+
+
+class Plot(object):
+    """Show graphical drawing of lines from their equation."""
+
+    def __init__(self):
+        self.setXAxis()
+        self.functs = []
+        self.verts = []
+
+    def prepare(self, line):
+        """Add the given line to the plot.
+        The line is not shown until the method show is called.
+
+        Args:
+            line: a triplet `(a, b, c)` representing the coefficients of the
+                line of equation `ax + bx + c = 0`.
+        """
+        a, b, c = line
+        if b == 0:
+            if a == 0:
+                raise ValueError('Not a line.')
+            else:
+                self.verts.append(line)
+        else:
+            self.functs.append(line)
+
+    def setXAxis(self, xmin=-10, xmax=10):
+        self.xmin = xmin
+        self.xmax = xmax
+
+    def reset(self):
+        self.setXAxis()
+        self.functs = []
+        self.verts = []
+
+    def plot(self, t, y, line):
+        a, b, c = line
+        plt.plot(t, y, label='%.4g*x + %.4g*y = %.4g' % (a, b, c))
+
+    def draw(self):
+        for a, b, c in self.functs:
+            t = np.array([self.xmin, self.xmax])
+            y = (-a * 1.0 / b) * t + (c * 1.0 / b)
+            self.plot(t, y, (a, b, c))
+        for a, b, c in self.verts:
+            x = c / a
+            self.plot([x, x], plt.ylim(), (a, b, c))
+        plt.axis('tight')
+        plt.legend()
+        plt.title('Exercices sur les droites')
+        plt.xlabel('x')
+        plt.ylabel('y')
+        plt.grid(True)
+
+    def save(self, filename):
+        self.draw()
+        plt.savefig(filename)
+
+    def show(self):
+        self.draw()
+        plt.show()
+
+
+if __name__ == '__main__':
+    p = Plot()
+    p.prepare((1, 1, 3))
+    p.prepare((-2, 1, -1))
+    p.prepare((1, 0, -5))
+    p.show()
+    input()