1. In sym-barchart.js, assign makeChart() result to an object and call it chart.
2. Modify getConfig() function so that x axis is attribute and y is value
3. Add a function to convert data object given by the PI Vision data layer to the format of the chart.
4. Call this function from dataupdate() and assign its result to the chart’s dataProvider property and run validateData().
Look at the map function documentation. Instead of showing the value at each point in time, return the difference between that value and the previous value