property="og:type" content="article" on Category

I found..

function change_wpseo_opengraph_type(){
    if ( is_front_page() || is_home() )
      return 'website';
    elseif (is_singular() || is_category())
        return 'article';
    else
        return 'object';

}
add_filter('wpseo_opengraph_type', change_wpseo_opengraph_type );

This is what I found more recently on the Yoast website. I’ve also modified it so that pages are properly set to og:type website, whereas posts are proerly set to og:type article. Using is_singular as in the prior comment would set both posts AND pages as og:type article which is not what I wanted for my purposes. Modify accordingly is you so choose.

function yoast_change_opengraph_type( $type ) {
    if ( is_front_page() || is_home() || is_page() )
      return 'website';
    elseif ( is_single() || is_category() )
        return 'article';
    else
        return 'object';

}
add_filter( 'wpseo_opengraph_type', 'yoast_change_opengraph_type' );