Move StatsProcedures to external dependency (#35)

Author: junyuan-chen

Project.toml

@@ -18,6 +18,7 @@ Reexport = "189a3867-3050-52da-a836-e630ba90ab69"
 StatsBase = "2913bbd2-ae8a-5f71-8c99-4fb6c76f3a91"
 StatsFuns = "4c63d2b9-4356-54db-8cca-17b64c39e42c"
 StatsModels = "3eaba693-59b7-5ba5-a881-562e759f1c8d"
+StatsProcedures = "d2f4e7c0-4966-47f3-9552-d63f8a71a436"
 StructArrays = "09ab397b-f2b6-538f-b94a-2f83cf4a842a"
 Tables = "bd369af6-aec1-5ad0-b16a-f7cc5008161c"
 
@@ -35,6 +36,7 @@ Reexport = "0.2, 1"
 StatsBase = "0.33"
 StatsFuns = "0.9"
 StatsModels = "0.6.18"
+StatsProcedures = "0.1"
 StructArrays = "0.5, 0.6"
 Tables = "1.2"
 julia = "1.3"

src/DiffinDiffsBase.jl

@@ -17,6 +17,8 @@ using StatsBase: CoefTable, Weights, stderror, uweights
 using StatsFuns: normccdf, norminvcdf, tdistccdf, tdistinvcdf
 @reexport using StatsModels
 using StatsModels: Schema
+@reexport using StatsProcedures
+using StatsProcedures: ≊, _args_kwargs, _parse!
 using StructArrays: StructArray
 using Tables
 using Tables: AbstractColumns, istable, columnnames, getcolumn
@@ -27,6 +29,7 @@ import Missings: allowmissing, disallowmissing
 import StatsBase: coef, vcov, confint, nobs, dof_residual, responsename, coefnames, weights,
     coeftable
 import StatsModels: concrete_term, schema, termvars, lag, lead
+import StatsProcedures: required, default, transformed, combinedargs, copyargs, _show_args
 
 # Reexport objects from StatsBase
 export coef, vcov, stderror, confint, nobs, dof_residual, responsename, coefnames, weights,
@@ -100,14 +103,6 @@ export cb,
        diff!,
        diff,
 
-       StatsStep,
-       AbstractStatsProcedure,
-       SharedStatsStep,
-       PooledStatsProcedure,
-       StatsSpec,
-       proceed,
-       @specset,
-
        CheckData,
        GroupTreatintterms,
        GroupXterms,
@@ -154,7 +149,6 @@ include("treatments.jl")
 include("parallels.jl")
 include("terms.jl")
 include("operations.jl")
-include("StatsProcedures.jl")
 include("procedures.jl")
 include("did.jl")