This may be a no brainer for those of you more familiar with AGOL: I created an AGOL map last year with 'last years data'. Now I have 'this years data' I would like to simply replace the old with the new, keeping my symbology. (The data has the same fields as last year). In addition to the map, I created a dashboard. If I'm able to update the map the dashboard 'looks at' will it be seamless?
I'd suggest either overwriting the feature layer with the new data like Katie suggested or using the append tool to add the new data to the existing dataset while filtering out your previous years data. Web maps and dashboards read the data and symbology from the item (layer item) and from the services url. If you use either overwrite or append, the itemID and service url remain the same, enabling a seamless transition once the underlying data is updated. The method you choose will really depend on the data that you want to store in ArcGIS Online, one year or multiple years.
I fiddled around a bit and added the new data to the original map and did a 'save as' to 'this-years-map' Turns out the data is a little more dyanmic year to year than I thought. I did look at the append and overwrite options as shown in the suggested help files.
