- Adds daily_growth and daily_growth_t instance attributes on Parameters class.

- Adds `daily_growth_helper` function to `src/penn_chime/parameters.py` to calculate daily growth rate as a function of doubling time.
- Updates `display_header` function in `src/penn_chime/presentation.py` to display initial and mitigated daily growth rates.
- Adds `test_daily_growth` test to `tests/test_app.py` to test above changes

Fixes #90

Author: Eric Smyth

src/penn_chime/presentation.py

@@ -60,10 +60,11 @@ def display_header(st, m, p):
     and Hospital market share (**{market_share:.0%}**).
 
 An initial doubling time of **{doubling_time}** days and a recovery time of **{recovery_days}** days imply an $R_0$ of
-**{r_naught:.2f}**.
+**{r_naught:.2f}** and daily growth rate of **{daily_growth:.2f}%**.
 
 **Mitigation**: A **{relative_contact_rate:.0%}** reduction in social contact after the onset of the
-outbreak **{impact_statement:s} {doubling_time_t:.1f}** days, implying an effective $R_t$ of **${r_t:.2f}$**.
+outbreak  **{impact_statement:s} {doubling_time_t:.1f}** days, implying an effective $R_t$ of **${r_t:.2f}$** and daily
+growth rate of **{daily_growth_t:.2f}%**..
 """.format(
             total_infections=m.infected,
             initial_infections=p.known_infected,
@@ -76,6 +77,8 @@ def display_header(st, m, p):
             r_naught=m.r_naught,
             doubling_time=p.doubling_time,
             relative_contact_rate=p.relative_contact_rate,
+            daily_growth=p.daily_growth,
+            daily_growth_t=p.daily_growth_t,
             r_t=m.r_t,
             doubling_time_t=abs(m.doubling_time_t),
             impact_statement=("halves the infections every" if m.r_t < 1 else "reduces the doubling time to")

tests/test_app.py

@@ -100,6 +100,16 @@ def test_mitigation_statement():
     st.cleanup()
 
 
+def test_daily_growth():
+    st.cleanup()
+    initial_growth = "and daily growth rate of **12.25%**."
+    mitigated_growth = "and daily growth rate of **1.18%**."
+    display_header(st, PARAM)
+    assert len((list(filter(lambda s: initial_growth in s, st.render_store))))
+    assert len((list(filter(lambda s: mitigated_growth in s, st.render_store))))
+    st.cleanup()
+
+
 st.cleanup()