How to NOT show sub categories?

Consider downloading and installing Otto’s PHP Code Widget.

Then put this in one of those widgets:

<?php wp_list_categories('depth=1'); ?>

See the template tag, wp_list_categories(), for more arguments including include= and exclude=

Thanks!
I will look more in depth because just adding <?php wp_list_categories(‘depth=1’); ?> to a php widget didn’t list the categories.