Iterate over array of hashes to sum values of one hash value based on another hash key - ruby

Question

I have the following array of hashes as input:
ar = [{"Sales"=>"11", "CustID"=>"Cust04"},
{"Sales"=>"44.9", "CustID"=>"Cust04"},
{"Sales"=>"79.17", "CustID"=>"Cust06"},
{"Sales"=>"73.84", "CustID"=>"Cust06"},
{"Sales"=>"34.9", "CustID"=>"Cust06"},
{"Sales"=>"29.6825", "CustID"=>"Cust06"},
{"Sales"=>"2048.7", "CustID"=>"Cust06"},
{"Sales"=>"15.24", "CustID"=>"Cust02"},
{"Sales"=>"54.874", "CustID"=>"Cust04"},
{"Sales"=>"12.79", "CustID"=>"Cust08"},
{"Sales"=>"22.65", "CustID"=>"Cust08"},
{"Sales"=>"63.26", "CustID"=>"Cust08"},
{"Sales"=>"16.207", "CustID"=>"Cust08"},
{"Sales"=>"782.2", "CustID"=>"Cust07"},
{"Sales"=>"215.45", "CustID"=>"Cust07"},
{"Sales"=>"781.23", "CustID"=>"Cust07"},
{"Sales"=>"370.14", "CustID"=>"Cust07"},
{"Sales"=>"1.7", "CustID"=>"Cust09"},
{"Sales"=>"22.405", "CustID"=>"Cust09"}
]
I am looking for an output as below, based on the total of sales, with a rank:
ar_out # =>
["Customer" => "Cust04", "TotalSales" => "xxxx", "Rank" => "1"]

Answer 1

You can try this way
Input
ar = [
{ "Sales" => "11", "CustID" => "Cust04" },
{ "Sales" => "44.9", "CustID" => "Cust04" },
{ "Sales" => "79.17", "CustID" => "Cust06" },
{ "Sales" => "73.84", "CustID" => "Cust06" },
{ "Sales" => "34.9", "CustID" => "Cust06" },
{ "Sales" => "29.6825", "CustID" => "Cust06" },
{ "Sales" => "2048.7", "CustID" => "Cust06" },
{ "Sales" => "15.24", "CustID" => "Cust02" },
{ "Sales" => "54.874", "CustID" => "Cust04" },
{ "Sales" => "12.79", "CustID" => "Cust08" },
{ "Sales" => "22.65", "CustID" => "Cust08" },
{ "Sales" => "63.26", "CustID" => "Cust08" },
{ "Sales" => "16.207", "CustID" => "Cust08" },
{ "Sales" => "782.2", "CustID" => "Cust07" },
{ "Sales" => "215.45", "CustID" => "Cust07" },
{ "Sales" => "781.23", "CustID" => "Cust07" },
{ "Sales" => "370.14", "CustID" => "Cust07" },
{ "Sales" => "1.7", "CustID" => "Cust09" },
{ "Sales" => "22.405", "CustID" => "Cust09" }
]
Proces
ar.each_with_object(Hash.new(0)) { |hsh, e| e[hsh['CustID']] += hsh['Sales'].to_f }.
sort_by { |_, v| -v }.
map.with_index { |(k, v), i| [{ 'Customer' => k, 'TotalSales' => v, 'Rank' => i + 1 }] }
Output
[
[
{
"Customer": "Cust06",
"TotalSales": 2266.2925,
"Rank": 1
}
],
[
{
"Customer": "Cust07",
"TotalSales": 2149.02,
"Rank": 2
}
],
[
{
"Customer": "Cust08",
"TotalSales": 114.90699999999998,
"Rank": 3
}
],
[
{
"Customer": "Cust04",
"TotalSales": 110.774,
"Rank": 4
}
],
[
{
"Customer": "Cust09",
"TotalSales": 24.105,
"Rank": 5
}
],
[
{
"Customer": "Cust02",
"TotalSales": 15.24,
"Rank": 6
}
]
]

Answer 2

ar.
each_with_object({}) do |hash, acc|
(acc[hash["CustID"]] ||= {"Customer" => hash["CustID"], "TotalSales" => 0}).
tap { |h| h["TotalSales"] += hash["Sales"].to_f }
end.
values.
sort_by { |h| -h["TotalSales"] }.
map.
with_index(1) { |h, idx| h.merge("Rank" => idx) }
#⇒ [{"Customer"=>"Cust06", "TotalSales"=>2266.2925, "Rank"=>1},
# {"Customer"=>"Cust07", "TotalSales"=>2149.02, "Rank"=>2},
# {"Customer"=>"Cust08", "TotalSales"=>114.90699999999998, "Rank"=>3},
# {"Customer"=>"Cust04", "TotalSales"=>110.774, "Rank"=>4},
# {"Customer"=>"Cust09", "TotalSales"=>24.105, "Rank"=>5},
# {"Customer"=>"Cust02", "TotalSales"=>15.24, "Rank"=>6}]