if you do not want to record every change on Temp Max/Min your code could populate a DataTable instead of recording the logged properties. then you would plot the datatable records in the Graph.
- Create a DataTable in TWX
- Create a datashape with Date (primary key)/TempMin/TempMax and associate it to the datatable
- Create a code that changes that Adds a row for the current date and updates it in case the temperature values change (subscription to temperature value should work)
- Add the QueryDatatableEntries to the mashup and link its AllDAta results to the chart.
- Configure the chart
Right, this is the best way to do it, I think. In step 3, in that service, just have it go to the DataTable and say "is there an entry for today?" if not, add it with the current values of temperature and humidity or whatever properties. If there is already a DataTable entry for the day, then just compare the current values of whatever properties with those in the DataTable, and if they are higher/lower than what is there, then update the DataTable with the new min and max values.
Hope this helps!