d3.group & join on NYTimes Covid-19 Data

Community Help
1

Hello!

I’ve run into relatively basic issue trying alter the raw data for the NYTimes Covid tracking on the county level. It is an array of objects that look like this:

https://raw.githubusercontent.com/nytimes/covid-19-data/master/us-counties.csv

[{"date":"2020-03-13","county":"Elmore","state":"Alabama","fips":"01051","cases":"1","deaths":"0","population":0}]

Here is my notebook:

I am trying to manipulate the array with my own county level data for Alabama, my home state. I have a .csv with population, demographics, and more to include in my graphic.

Unfortunately, I cannot find the right way to do the data join so that all the array entries from a county also populate with the new data.

I have never used d3 selection before and am having difficulty applying it to this massive data set.

Any help would be appreciated. I can explain the problem in more detail, but this is not a specific bug. I have tried many approaches, none of which quite get the job done.

2

A Map is often useful for this. d3.group will create nested maps for you, but you can also construct them directly like so:

popByCounty = new Map(al_county_pop.map(d => [d.county, d.population]))

Then later when you want to get the population for a specific county in Alabama, you can say:

popByCounty.get("Jefferson")

If you want to join this together with the NYT data, you could also say:

raw_county_data
  .filter(a => a.state === "Alabama")
  .map(d => ({...d, population: popByCounty.get(d.county)}))
1 Like
3

Incredible…

Thank you!