Saving results

Let's say that you've run a chain and want to save the resulting ChainScoreData object to your hard drive, so that you can do analysis of the results at a later time without having to re-run the chain. Below are some options you could pursue to do that.

• GerryChain.save_scores_to_csv
• GerryChain.save_scores_to_json

Serialization

One super simple way to save the results is to use Julia's built-in Serialization library to save the ChainScoreData object. Here's an example:

chain_data = recom_chain(...)
serialize("example.jld", chain_data)

Then, in order to read back the saved data in another file, just run

chain_data = deserialize("example.jld")

Note that the .jld format is specific to Julia, so you won't be able to deserialize in a script written in another language, like Python or R.

Saving scores to CSV

CSV is a common format used to store data. We've written a function called save_scores_to_csv() into GerryChain that makes it super simple to export scores to a CSV format, which can then be read by programs in any language of your choosing. Each row of the CSV will correspond to one state in the chain, while each score corresponds to one or more columns. (District level scores will produce one column for each district. For example: a district-level score called bvap evaluated on plans with 10 districts will generate 10 columns: bvap_1, bvap_2, ...bvap_10.) The order of the rows corresponds to the order of the states visited by the chain. Here's what the function looks like:

save_scores_to_csv(filename::String,
                   chain_data::ChainScoreData,
                   score_names::Array{String,1}=String[])

Usage

# let's say there are 3 districts and 2 steps in the chain
chain_data = recom_chain(...)
save_scores_to_csv("data.csv", chain_data, score_names = ["cut_edges", "vote_count_d", "vote_share_d"]) # 1 plan score, 2 district-level scores

Resulting CSV

cut_edges,vote_count_d_1,vote_count_d_2,vote_count_d_3,vote_share_d_1,vote_share_d_2,vote_share_d_3
5,2,4,4,0.2,0.4,0.4
6,3,5,2,0.3,0.5,0.2

Saving scores to JSON

save_scores_to_json(filename::String,
                    chain_data::ChainScoreData,
                    score_names::Array{String,1}=String[])

Usage

chain_data = recom_chain(graph, partition, pop_constraint, 10, scores)
save_scores_to_json("test.json", chain_data) # by default will save all scores in the chain
# alternatively, save_scores_to_json("test.json", chain_data, ["names", "of", "desired", "scores"])