check for update and append functions

[kyle-messier]

As part of the pipeline for updating the analysis with new data, we will need functions that:

• [ ] Check for updates in data
• [ ] Append to existing datasets (both air quality and covariates)

[sigmafelix]

Some points to consider --

1. Per our initial study period, we already have new data to ingest at least in some datasets.
2. How do we define whether a certain dataset is updated and ready to ingest? A few days, full 6 months ahead, or the entire year?
3. Most of the datasets are updated regularly (e.g., MODIS has 1-16 days, HMS has 1 day, NLCD has two years, etc.)
4. Is the check for update supposed to be a part of the pipeline?

[kyle-messier]

@sigmafelix I think in v1.0 we just need to update everything according the the bi-annual updates of EPA AQS data. And I do think we want the check update code to be part of the pipeline.

[kyle-messier]

@sigmafelix targets and the tarchetypes package have specific targets for listening and updating the pipeline based on the age of the data/target.

https://docs.ropensci.org/tarchetypes/reference/index.html#cues

[sigmafelix]

@kyle-messier I will add tar_cue_age() in tarchetypes to all download targets in the pipeline. Now I am working on running the pipeline part by part with small datasets.