function createRandomData() {
    var numDataItems = Math.floor((Math.random() * 10) + 1);
    var d = [];
    for (var i = 0; i < numDataItems; i++) {
        d.push(Math.floor((Math.random() * 50) + 1));
    }
    return d;
}


function update() {
    var exampleData = createRandomData();

    var visElement = d3.select('#vis');

    var paras = visElement.selectAll('p')
        .data(exampleData);

    paras
        .exit()
        .remove();

    var new_paras = paras
        .enter()
        .append('p');

    new_paras.merge(paras)
        .text(function(d, i) {
            return "this is paragraph " + i + " and the data value is " + d;
        });

}

update();