Get Favourite day from data set - cloudant

Question

I have data like this
State City Day
Arizona Chandler Monday
Arizona Mesa Wednesday
Arizona Chandler Monday
Arizona Mesa Saturday
Washington Vancouver Friday
Washington Vancouver Friday
Washington Spokane Monday
Washington Vancouver Tuesday
Washington Spokane Monday
I want to get favourite day by state and city
eg Favourite day for Washington-Vancouver is Friday and that for Arizon-Chandler is Monday

Answer 1

You should look into using views. You could create your map function to emit the key as [state, city, day] with a value of 1 you could then use the _count reduce to see how many times each key is mentioned. From that you will be able to determine the favourite day for each state / city. You can read more about views in the cloudant documentation.

Answer 2

So in JSON a document would look like this:
{
"state": "Arizona",
"city": "Chandler",
"day": "Monday"
}
To find "favourite day by state and city" we can create an index where the key comprises of all three things:
function(doc) {
emit([doc.state,doc.city,doc.day], null);
}
And use the built-in _count reducer.
This will give keys like this:
["Arizona","Chandler","Monday"]
The counts then then be collected by interrogating the view:
/db/_design/mydesigndoc/_view/myview?group_level=3
which will give counts for each distinct combination of state/city/day.
It can't just return the "favourite"; only all the unique combinations and you would have to iterate through the result set to find the one with largest total.