From e73f193667766857cedc7b3f237d2accb008b409 Mon Sep 17 00:00:00 2001
From: Arthur <contactaguo@gmail.com>
Date: Sat, 15 Oct 2016 15:20:18 -0400
Subject: [PATCH 1/2] test pull request

---
 test.py | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 test.py

diff --git a/test.py b/test.py
new file mode 100644
index 0000000..45a72c4
--- /dev/null
+++ b/test.py
@@ -0,0 +1 @@
+print("testing pull")

From 2f225476f3cf4f8dfc22a8f925d42354cbf2c256 Mon Sep 17 00:00:00 2001
From: Arthur <contactaguo@gmail.com>
Date: Sat, 15 Oct 2016 15:54:47 -0400
Subject: [PATCH 2/2] real submission

---
 hw-lightning.py | 52 +++++++++++++++++++++++++++++++++++++++++++++++++
 test.py         |  1 -
 2 files changed, 52 insertions(+), 1 deletion(-)
 create mode 100644 hw-lightning.py
 delete mode 100644 test.py

diff --git a/hw-lightning.py b/hw-lightning.py
new file mode 100644
index 0000000..ff8b6ca
--- /dev/null
+++ b/hw-lightning.py
@@ -0,0 +1,52 @@
+def getMwr(allSnaps):
+    '''
+    Uses Newtons method for finding IRR/mwr #UW MATH represent
+    It converges quadratically aka it's pretty fast :)
+
+    I was gonna use brent's method but that's not as clear. 
+    I decided to use Newton's since it's much clearer code wise
+    '''
+    numIterations=0
+    maxIterations=400
+    allowedError=0.0001 #10x the precision
+
+    prevGuess=[1, 0] #prevGuess[0] = 2nd last guess, prevGuess[1] = last guess
+    finalMarketValue=allSnaps[-1][2]
+    numPeriods = len(allSnaps)
+
+    while(abs(prevGuess[0] - prevGuess[1]) > allowedError):
+        prevGuess[0] = prevGuess[1]
+        derivRate = derivIrr(allSnaps, prevGuess[0], numPeriods)
+        eir = (evalIrr(allSnaps, prevGuess[0], numPeriods)-finalMarketValue)
+        #Will cause div zero error, and having a zero derivRate means you 
+        #contribute nothing but gained market value (money from thin air?)
+        if (derivRate == 0):
+            return "undefined"
+        prevGuess[1] = prevGuess[0] - eir / derivRate
+        numIterations+=1
+        #Too many iterations probably means non-convergence
+        if (numIterations > maxIterations):
+            return "undefined"
+    return prevGuess[1]
+
+def evalIrr(allSnaps, testIrr, numYears):
+    retVal = 0 
+    for year, cf, mv in allSnaps:
+        retVal += cf*(1+testIrr)**(numYears-year-1)
+    return retVal
+
+def derivIrr(allSnaps, testIrr, numYears):
+    retVal = 0
+    for year, cf, mv in allSnaps:
+        retVal += (numYears-year-1)*cf*(1+testIrr)**(numYears-year-2)
+    return retVal
+
+f = open('test.csv', 'r')
+
+#Parsing
+#convert input into nested list
+allSnaps = []
+for snapshot in f.read().split()[1:]: #ignore line 0 b/c it's not numbers 
+    allSnaps.append([float(number) for number in snapshot.split(",")])
+
+print(getMwr(allSnaps))
diff --git a/test.py b/test.py
deleted file mode 100644
index 45a72c4..0000000
--- a/test.py
+++ /dev/null
@@ -1 +0,0 @@
-print("testing pull")