I don't know exactly what you are meaning with a "two dimensional vector" (as far as I understand a vecor is always one dimensional, but can contain another vector..), but here is an example:
<?xml version="1.0" encoding="UTF-8"?>
<xp:view xmlns:xp="http://www.ibm.com/xsp/core">
<xp:this.dataContexts>
<xp:dataContext var="data">
<xp:this.value><![CDATA[#{javascript:var i=0;
var j=0;
var data:java.util.Vector = new java.util.Vector();
for( i=0; i<5; i++){
var hlp:java.util.Vector = new java.util.Vector();
for(j=0;j<5+i;j++){
hlp.add( j );
}
data.add( hlp );
}}]]></xp:this.value>
</xp:dataContext>
</xp:this.dataContexts>
<xp:repeat id="repeat1" rows="30" var="rowsVar" value="#{javascript:data}">
<xp:repeat id="repeat2" rows="30" var="colsVar" value="#{javascript:rowsVar}">
<xp:text escape="true" id="computedField1" value="#{javascript:colsVar}"></xp:text> 
</xp:repeat>
</xp:repeat>
</xp:view>
Hope this helps
Sven