Create a submission script

[stephenturner]

After getting all the necessary components down, need to create a submission workflow script that will:

1. bring in necessary data (get hosp and vax data #1 get hosp and vax data #2 bring in ili and hosp data from cdcfluview #5)
2. do any necessary covariate forecasting (forecast ILI #23)
3. fit models (glm #24)
4. format for submission (Forecast submission formatting #10)
5. validate forecasts (forecast validation #12)
6. visualize forecasts (Function to visualize forecasts #11)
7. stick it in a submission subdirectory with metadata (Model metadata.txt #16), and add to .Rbuildignore

For reference:

• See how this is handled in focustools: https://github.com/signaturescience/focustools/#covid-19-forecast-hub-submissions
• Focustools submission script: https://github.com/signaturescience/focustools/blob/master/submission/submission.R

[stephenturner]

see also #60