How not to display ALL items of a database

Question

When I select a category from the head navigation bar in a database http://www.taracomplementos.com/tara/, the default display is all the items of the DB, and you must select one of the categories inside of the page to see related articles. I wish I knew how to have displayed ONLY the items belonging to a specific category. I think that the trick must be in these lines, but I can't figure out how to modify it:

        <div class="sort">
        <ul id="portfolio-control">
            <li class="segment-1"><!-- changed All for todo --><a class="active all" data-value="all" href="#"><?php _e('todo', 'ux') ?></a></li>
            <?php wp_list_categories(array('title_li' => '', 'exclude' => $excludecat,'taxonomy' => 'skill-type', 'walker' => new Walker_Category_Filter())); ?>
        </ul>
    </div>
    <?php endwhile; else : endif; ?>
</div>
<div class="span16 gallery">
    <?php $args = array(
       'post_type' => 'portfolio',
       'orderby'=>'menu_order',
       'order'     => 'ASC',
       'posts_per_page' => '-1',
       'skill-type' => get_query_var('skill-type'),
       'tax_query' => array(
       array(
               'taxonomy' => 'skill-type',
               'field' => 'id',
               'terms' => $excludecat,
               'operator' => 'NOT IN',
               )
           ) // end of tax_query
       );
    ?>
    <?php $query = new WP_Query($args); ?>

Can anybody help me? TIA, guido

Answer 1

Check if excludecat is containing category IDs or category slugs, if it is using slugs/text then change the ID field to slug.

Also define the relation to use, e.g.:

'relation' => 'AND',

Here are the parameters: http://codex.wordpress.org/Class_Reference/WP_Query#Taxonomy_Parameters