From 2c5c651e995f9684833f2c41ab051708b0f4ed5f Mon Sep 17 00:00:00 2001
From: Grant Sanderson <grantsanderson7@gmail.com>
Date: Wed, 21 Feb 2018 13:13:24 -0800
Subject: [PATCH] Gives fourier graphs created with FFT and underlying function
 attribute

---
 active_projects/fourier.py | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/active_projects/fourier.py b/active_projects/fourier.py
index 1c7fd54c..c725d148 100644
--- a/active_projects/fourier.py
+++ b/active_projects/fourier.py
@@ -59,6 +59,13 @@ def get_fourier_graph(
         for x, y in zip(frequencies, fft_output[:n_samples//2])
     ])
     graph.highlight(color)
+    f_min, f_max = [
+        axes.x_axis.point_to_number(graph.points[i])
+        for i in 0, -1
+    ]
+    graph.underlying_function = lambda f : axes.y_axis.point_to_number(
+        graph.point_from_proportion((f - f_min)/(f_max - f_min))
+    )
     return graph
 
 def get_fourier_transform(