Get all fields within Matrix for position?
If I'm understanding what you've asked correctly (and there's every chance I'm not – it's been a long day), I've got something similar on one of my sites and I'm using the following code:

{% for faq in entry.faq if faq.column == 'Left' %}
    &lt;li&gt;
        &lt;h3&gt;{{ faq.question }}&lt;/h3&gt;
        &lt;p&gt;{{ faq.answer }}&lt;/p&gt;
    &lt;/li&gt;
{% endfor %}


then:

{% for faq in entry.faq if faq.column == 'Right' %}
    &lt;li&gt;
        &lt;h3&gt;{{ faq.question }}&lt;/h3&gt;
        &lt;p&gt;{{ faq.answer }}&lt;/p&gt;
    &lt;/li&gt;
{% endfor %}


In this case 'faq' is the Matrix field and 'faq.column' is the Position Select field.

There are neater ways to do this to avoid the repeated code, but you get the idea.