Average value of fields in wordpress posts

All my posts has a rating of 1-5 and on my category page I want to display the average rating of all the posts of that category. So I kno开发者_C百科w where the field with the value is within the post loop, but how can I get those values and calculate the average outside the post loop?

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The easiest solution is probably to construct an array during the loop and average it at the end.

// Before the loop

$ratings = array();

// During the loop

$ratings[] = $post_rating;

// After the loop

$average = array_sum($ratings) / count($ratings);