How to choose variables from a list for a function and then use the solution in a subsequent function?

Question

I am trying to calculate heating degree days and cooling degree days and output that information to a table. I am using mathematica's curated data to do this. In text this is what I would like to do. Use a city name to collect weather data (the mean temp for every day of a certain year), then calculate the HDD and CDD and to create a cumulative value of hdd and cdd for the entire year. I want to use the city name to collect a value for country name, country gdp, and city population. I have used a demonstration project to try and figure this out but I am stuck at this point. I have the following already worked out.

Module[
 {dateRange, mean, cdd, hdd, station, country, location, population, 
  GDPPerCapita,
  reference = (65 - 32)/1.8, cumList},
 station = "Chicago";
 country = CityData[station, "Country"];
 population = CityData[station, "Population"];
 location = CityData[station, "Coordinates"];
 GDPPerCapita = CountryData[country, "GDPPerCapita"];
 dateRange = {{2011, 1, 1}, {2011, 12, 31}, "Day"};
 mean = WeatherData[station, "MeanTemperature", dateRange];
 cdd = Join[Transpose[{mean[[All, 1]]}], 
   Transpose[{Max[# - reference, 0] & /@ mean[[All, 2]]}], 2];
 hdd = Join[Transpose[{mean[[All, 1]]}], 
   Transpose[{Max[reference - #, 0] & /@ mean[[All, 2]]}], 2];
 cumList = Transpose[{Join[
     Transpose[{cdd[[All, 1]]}],
     Transpose[{Drop[FoldList[Plus, 0, cdd[[All, 2]] + hdd[[All, 2]]],
         1]}],
     2]}];
 Grid[station, country, location, population, GDPPerCapita, 
  Last[cumList]]]

In this particular example I used a set city name ie station = "Chicago". When I do this it returns the correct result for that specific city, in a grid in this case..

Grid["Chicago", "UnitedStates", {41.8376, -87.6818}, 2695598, 
  45230.2, {{{2011, 12, 31}, 3935.4}}]

I want the variables to be chosen from a list of cities....

cityLIST = CityData[#, "Name"] & /@ CityData[];

So basically I want to run this or something like it for every string in a list, and output the results to a table. I am new to mathematica, this is the first thing I have ever tried. If anyone has a minute to help me out with this I would really appreciate it.

Thanks

Answer 1

A slight modification of your code makes this a real function:

myWeatherData[station_] :=
 Module[{dateRange, mean, cdd, hdd, country, location, population, 
         GDPPerCapita, reference = (65 - 32)/1.8, cumList},
   country = CityData[station, "Country"];
   population = CityData[station, "Population"];
   location = CityData[station, "Coordinates"];
   GDPPerCapita = CountryData[country, "GDPPerCapita"];
   dateRange = {{2011, 1, 1}, {2011, 12, 31}, "Day"};
   mean = WeatherData[station, "MeanTemperature", dateRange];
   cdd = Join[Transpose[{mean[[All, 1]]}], 
              Transpose[{Max[# - reference, 0] & /@ mean[[All, 2]]}], 2];
   hdd = Join[Transpose[{mean[[All, 1]]}], 
              Transpose[{Max[reference - #, 0] & /@ mean[[All, 2]]}], 2];
   cumList =  Transpose[{Join[Transpose[{cdd[[All, 1]]}], 
                         Transpose[{Drop FoldList[Plus, 0, cdd[[All, 2]] + 
                          hdd[[All, 2]]], 1]}], 2]}];
   {station, country, location, population, GDPPerCapita, Last[cumList]}
 ]

The city list

cityLIST = CityData[#, "Name"] & /@ CityData[];

It is pretty long:

 cityLIST // Length

(* ==>  164186  *)

Therefore, we'll try it on the first ten cities in the list:

Grid[myWeatherData /@ cityLIST[[1 ;; 10]], Frame -> All]

Answer 2

You need to define a function like this

(* 
We use StringQ in the variable pattern so that it takes only strings of city names.
Without the StringQ it will also work!
*)
MyDataCollecter[station_?StringQ] := 
Module[{dateRange, mean, cdd, hdd, country, location, population, 
GDPPerCapita, reference = (65 - 32)/1.8, cumList},
country = CityData[station, "Country"];
population = CityData[station, "Population"];
location = CityData[station, "Coordinates"];
GDPPerCapita = CountryData[country, "GDPPerCapita"];
dateRange = {{2011, 1, 1}, {2011, 12, 31}, "Day"};
mean = WeatherData[station, "MeanTemperature", dateRange];
cdd = Join[Transpose[{mean[[All, 1]]}], 
 Transpose[{Max[# - reference, 0] & /@ mean[[All, 2]]}], 2];
hdd = Join[Transpose[{mean[[All, 1]]}], 
 Transpose[{Max[reference - #, 0] & /@ mean[[All, 2]]}], 2];
cumList = 
Transpose[{Join[Transpose[{cdd[[All, 1]]}], 
   Transpose[{Drop[
      FoldList[Plus, 0, cdd[[All, 2]] + hdd[[All, 2]]], 1]}], 2]}];
(* For the look *)
Grid[{ToString[#] & /@ {Station, Country, Coordinate, Population, 
   GDP, CumList}, {station, country, location, population, 
  GDPPerCapita, Grid[Last[cumList], Frame -> All]}}, Frame -> All,
 ItemStyle -> "Subsection", Background -> {None, {Pink, Cyan}}]];
(* To make the function accept a list of city names *)
SetAttributes[MyDataCollecter, Listable];

Now we apply this function on a randomly chosen list of of ten cities from your list of cities cityLIST.

MyDataCollecter@RandomChoice[cityLIST, 10] // TableForm

But I hope you will notice that for many cities there is no data in the Wolfram Database and that why MMA can report an error called WeatherData::notent:. Here is an example.

WeatherData::notent: "\!\(\"\\\"Kumbi\\\"\"\) is not a known entity, 
class, or tag for  WeatherData. Use WeatherData[] for a list of entities."

I suggest that you look at the answers of this post on how to adapt your code when such error occurs.

BR