You could use the following js method to generate charttable's chart:

<script>
    myChartTable.generateChart(); // "myChartTable" is ChartTable php widget's name/id
</script>

Of course a label column and some data columns must be selected first for the chart to be generated correctly. You could also set those columns' selected values like this:

    $(myChartTable.labelColumnSel).val( [ "myLabelColumn" ] );
    $(myChartTable.dataColumnsSel).val( [ "myDataColumn1", "myDataColumn2" ] );
    ...
    myChartTable.generateChart(); // "myChartTable" is ChartTable php widget's name/id

Just put the code in my previous code in your report view file where ChartTable widget is:

ChartTable::create(array(
    "name" => "myChartTable",
    ...
    "onReady" => "autoGenerateChart",
));
<script>
    function autoGenerateChart() {
        $(myChartTable.labelColumnSel).val( [ "myLabelColumn" ] ); // change this to your label column name
        $(myChartTable.dataColumnsSel).val( [ "myDataColumn1", "myDataColumn2" ] ); // change these to all of your data column names       
        myChartTable.generateChart(); // "myChartTable" is ChartTable php widget's name/id
    }
</script>