How To Sum Certain Array Values?

[anevins]

Hi all,

 

What I'm trying to do is get the average of sentiment values for each City in the UK.

I have an array of all the cities in the UK, with sentiment values for each city.

 

-- Tricky to say, sorry --

Cities can appear more than once, so I want to find the average sentiment for that city, then construct/ return an array with just those cities and their sentiment (that has been averaged for all occurrences of that city).

 

This is an excerpt of my array

array (size=1871)
 0 => 
   array (size=2)
     'name' => string 'Cardiff' (length=7)
     'sentiment' => string '2.72' (length=4)
 1 => 
   array (size=2)
     'name' => string 'London' (length=6)
     'sentiment' => string '4.24' (length=4)
 2 => 
   array (size=2)
     'name' => string 'Birmingham' (length=10)
     'sentiment' => string '3.415' (length=5)
 3 => 
   array (size=2)
     'name' => string 'Birmingham' (length=10)
     'sentiment' => string '3.34' (length=4)

and so forth.

 

With Birmingham, for example, I want to add up 3.415 with 3.34, divide by 2 and then return just the one occurrence of "Birmingham" and its averaged sentiment. I want to do this for each city, so there is only one occurrence for each city, in another array.

 

Does anyone know how I might go about this?

Edited November 27, 2012 by anevins

[requinix]

First step I would take is building up an array that looked like

array(
"Cardiff" => array(
	"total" => 2.72,
	"count" => 1
),
"London" => array(
	"total" => 4.24,
	"count" => 1
),
"Birmingham" => array(
	"total" => 6.755,
	"count" => 2
)
)

[Christian F.]

Is this array fetched from a database somewhere? If so, then you can use the DB to do the calculations for you.

 

Just a quick example:

SELECT AVG(`sentiment`), `name` FROM `city_sentiment` GROUP BY `city_id`;

Edited November 27, 2012 by Christian F.