Historical values are saved in the database, just like the Datalogger data. You will simply need to run queries against the proper tables. Then populate the array tags with those values.
Trend Charts do the queries for you automatically, as well as graph the data that is coming in. With the Chart component you will need to manually handle the charting of the data. You could always use a Datalogger to gather the data you want, and then use the Chart to plot it. If you wanted to, you could recreate the functionality of a Trend Chart with History turned on using a Datalogger and a Chart. Then you have more control of what gets plotted.
Beijer Electronics, Inc. | Applications Engineer