Add a link to download full tabular data as CSV

Author: Nick Canzoneri

src/app.py

@@ -4,6 +4,7 @@
 import streamlit as st  # type: ignore
 
 from penn_chime.presentation import (
+    build_download_link,
     display_header,
     display_sidebar,
     draw_census_table,
@@ -53,6 +54,12 @@
 
 if st.checkbox("Show Projected Admissions in tabular form"):
     draw_projected_admissions_table(st, admissions_df, as_date=p.as_date)
+    build_download_link(st,
+        filename="projected_admissions.csv",
+        df=admissions_df,
+        parameters=p
+    )
+
 st.subheader("Admitted Patients (Census)")
 st.markdown(
     "Projected **census** of COVID-19 patients, accounting for arrivals and discharges at Penn hospitals"
@@ -64,6 +71,11 @@
 st.markdown(chart_descriptions(census_chart, suffix=" Census"))
 if st.checkbox("Show Projected Census in tabular form"):
     draw_census_table(st, census_df, as_date=p.as_date)
+    build_download_link(st,
+        filename="projected_census.csv",
+        df=census_df,
+        parameters=p
+    )
 st.markdown(
     """**Click the checkbox below to view additional data generated by this simulation**"""
 )

src/penn_chime/presentation.py

@@ -7,7 +7,7 @@
 import pandas as pd  # type: ignore
 
 from .defaults import Constants, RateLos
-from .utils import add_date_column
+from .utils import add_date_column, dataframe_to_base64
 from .parameters import Parameters
 
 DATE_FORMAT = "%b, %d"  # see https://strftime.org
@@ -440,3 +440,17 @@ def draw_raw_sir_simulation_table(st, parameters):
         )
 
     st.table(infect_table)
+    build_download_link(st,
+        filename="raw_sir_simulation_data.csv",
+        df=projection_area,
+        parameters=parameters
+    )
+
+def build_download_link(st, filename: str, df: pd.DataFrame, parameters: Parameters):
+    if parameters.as_date:
+        df = add_date_column(df, drop_day_column=True, date_format="%Y-%m-%d")
+
+    csv = dataframe_to_base64(df)
+    st.markdown("""
+        <a download="{filename}" href="data:file/csv;base64,{csv}">Download full table as CSV</a>
+""".format(csv=csv,filename=filename), unsafe_allow_html=True)

src/penn_chime/utils.py

@@ -3,6 +3,7 @@
 from collections import namedtuple
 from datetime import datetime, timedelta
 from typing import Optional
+from base64 import b64encode
 
 import numpy as np  # type: ignore
 import pandas as pd  # type: ignore
@@ -65,3 +66,15 @@ def add_date_column(
     df = df[date_columns + non_date_columns]
 
     return df
+
+def dataframe_to_base64(df: pd.DataFrame) -> str:
+    """Converts a dataframe to a base64-encoded CSV representation of that data.
+
+    This is useful for building datauris for use to download the data in the browser.
+
+    Arguments:
+        df: The dataframe to convert
+    """
+    csv = df.to_csv(index=False)
+    b64 = b64encode(csv.encode()).decode()
+    return b64