how can i make edites to the attribute table of layer that is a duplicate without effecting the origional layer.

[joshuaaranda]

I have created a layer contaning data of all the tornados to occur in california since 1950. I have duplicated this layer. so there are two layers in my content pane - Cal_torn_map (the original) and ElninoTornados (the duplicate) 

what i am trying to do is make changes to the duplicate to show only tornados from specific years, as opposed to showing all tornados like the original.  

The way i was trying to do this is delete data from the attribute table of the duplicate to remove the points from the years i dont want, but when i do, points from the original are also deleted. 

Is there a way i can make changes to the duplicate without effecting the original?

[ChrisDonohue__GISP]

Assuming you are using ArcGIS Desktop, what I suspect has happened so far is that you copied the layer in the Table of Contents, which appears to have created a new layer but actually just creates another link back to the same single dataset.  So at this point you have two choices - either use a Query to modify what is being displayed for each layer shown, or make an actual permanent copy of the data and edit that.

If you want to go the query route, right-click on the layer, Properties, then Definition Query tab.  Then in the area below define a query to affect the data displayed.  Given the example you stated, it probably would be something like YEAR = 2014,

As for the create a new permanent layer route, go to the feature class in the Table of Contents, right-click, Data, Export Data

Exporting features—Help | ArcGIS for Desktop 

Chris Donohue, GISP

[curtvprice]

Chris is correct. A map layer is just an object that does not contain data but information needed to access data (including the source location - where the data really is, symbology, definition query that selects which data to include, etc). The layer does not have data actually in it -- it just points to a dataset somewhere.