adding fix to refresh derived values when loading json data, closes #64 (#65)

* adding fix to refresh derived values when loading json data, closes #64

* added a note to the readme on calling update_derived_values

Author: ccoffrin

README.md

@@ -81,6 +81,7 @@ run_opf(network_data, ACPPowerModel, IpoptSolver())
 
 network_data["bus"][3]["pd"] = 0.0
 network_data["bus"][3]["qd"] = 0.0
+update_derived_values(network_data)
 
 run_opf(network_data, ACPPowerModel, IpoptSolver())
 ```

src/core/data.jl

@@ -1,5 +1,6 @@
 # tools for working with PowerModels internal data format
 
+export update_derived_values
 
 # adds values that are derived from other values in PM data structure, for the first time
 function add_derived_values(data::Dict{AbstractString,Any})

src/io/common.jl

@@ -2,6 +2,8 @@ function parse_file(file)
     if endswith(file, ".m")
         return PowerModels.parse_matpower(file)
     else
-        return PowerModels.parse_json(file)
+        network_data = PowerModels.parse_json(file)
+        update_derived_values(network_data)
+        return network_data
     end
 end