let $numbins := 10
let $binsize := 1.0 div $numbins
let $models := doc('all.xml')//model[psauc != "None"]
let $total := count($models)
for $index in (0 to $numbins)
    let $lobound := ($index - 1)*$binsize
    let $hibound := ($index)*$binsize
    let $count := count($models[psauc > $lobound and psauc <= $hibound])
    return
        <value lo="{$lobound}" hi="{$hibound}">
            <count>{$count}</count>
            <fraction>{$count div $total}</fraction>
        </value>