Wordpress generate plugin install URL

functions.php

<?php

/**
 * http://stackoverflow.com/questions/5327920/how-to-generate-a-wordpress-plugin-install-link
**/

$action = 'install-plugin';
$slug = 'akismet';
wp_nonce_url(
    add_query_arg(
        array(
            'action' => $action,
            'plugin' => $slug
        ),
        admin_url( 'update.php' )
    ),
    $action.'_'.$slug
);

?>