Most viewed posts from [YEAR] using the WordPress Popular Posts plugin

functions.php

<?php
/**
 * Registers shortcode [wpp_top_viewed_posts_from].
 *
 * This function registers a new custom shortcode that
 * outputs the top viewed posts of a given year.
 *
 * Requires PHP 5.3+ to work.
 *
 * @author  Hector Cabrera (cabrerahector.com)
 * @param   array   $atts
 * @return  string
 */
function wpp_top_viewed_posts_from( $atts ) {
    $args = shortcode_atts( array(
        'year' => date('Y')
    ), $atts );

    $key = 'wpp_top_viewed_' . md5(serialize($atts));
    $top_posts = get_transient($key);

    if ( false === $top_posts ) {

        $join_filter = function($join) use ($args) {
            global $wpdb;
            return "INNER JOIN (SELECT SUM(pageviews) AS pageviews, postid FROM `{$wpdb->prefix}popularpostssummary` WHERE view_datetime BETWEEN '{$args['year']}-01-01 00:00:00' AND '{$args['year']}-12-31 23:59:59' GROUP BY postid) v ON p.ID = v.postid";
        };

        add_filter( 'wpp_query_join', $join_filter );
        $top_posts = do_shortcode('[wpp range=custom]');
        remove_filter( 'wpp_query_join', $join_filter );

        set_transient($key, $top_posts, 1 * DAY_IN_SECONDS); // cache for 1 day
    }

    return $top_posts;
}
add_shortcode( 'wpp_top_viewed_posts_from', 'wpp_top_viewed_posts_from' );