From 84213ab8cd27369f796131c68c075f12f8bd0ce2 Mon Sep 17 00:00:00 2001
From: Maxime Beauchemin <maximebeauchemin@gmail.com>
Date: Wed, 17 Aug 2016 12:26:10 -0700
Subject: [PATCH] [line] growth vs factor option for 'Period Ratio' (#970)

* [line] growth vs factor option for 'Period Ratio'

* i18n
---
 caravel/forms.py | 12 ++++++++++++
 caravel/viz.py   | 11 +++++++++--
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/caravel/forms.py b/caravel/forms.py
index c06565d23a..5de93cf830 100755
--- a/caravel/forms.py
+++ b/caravel/forms.py
@@ -817,6 +817,18 @@ class FormFactory(object):
                     "[integer] Number of period to compare against, "
                     "this is relative to the granularity selected")
             }),
+            'period_ratio_type': (SelectField, {
+                "label": _("Period Ratio Type"),
+                "default": 'growth',
+                "choices": (
+                    ('factor', _('factor')),
+                    ('growth', _('growth')),
+                    ('value', _('value')),
+                ),
+                "description": _(
+                    "`factor` means (new/previous), `growth` is "
+                    "((new/previous) - 1), `value` is (new-previous)")
+            }),
             'time_compare': (TextField, {
                 "label": _("Time Shift"),
                 "default": "",
diff --git a/caravel/viz.py b/caravel/viz.py
index 11179712a6..5413abb859 100755
--- a/caravel/viz.py
+++ b/caravel/viz.py
@@ -997,7 +997,7 @@ class NVD3TimeSeriesViz(NVD3Viz):
         'fields': (
             ('rolling_type', 'rolling_periods'),
             'time_compare',
-            'num_period_compare',
+            ('num_period_compare', 'period_ratio_type'),
             None,
             ('resample_how', 'resample_rule',), 'resample_fillmethod'
         ),
@@ -1038,7 +1038,14 @@ class NVD3TimeSeriesViz(NVD3Viz):
         num_period_compare = form_data.get("num_period_compare")
         if num_period_compare:
             num_period_compare = int(num_period_compare)
-            df = (df / df.shift(num_period_compare)) - 1
+            prt = form_data.get('period_ratio_type')
+            if prt and prt == 'growth':
+                df = (df / df.shift(num_period_compare)) - 1
+            elif prt and prt == 'value':
+                df = df - df.shift(num_period_compare)
+            else:
+                df = df / df.shift(num_period_compare)
+
             df = df[num_period_compare:]
 
         rolling_periods = form_data.get("rolling_periods")