previous topic   |   home   |   next topic

Main Menu - Themes Buttons

Copy Theme button

Before you make major changes to a theme, you should make a copy to edit so that if you make a mistake you will have the original as a backup. This button works like the Theme-->Convert To Shapefile menu choice that is visible when the active document is a View, except at the end it will tell you how many of the features were copied. If you have features selected, only the selected features will be copied to the new theme, so make sure none are selected by clicking the ArcView Clear Selected Features button before you copy if you want to copy the entire theme. It is recommended that you copy your themes often. You can also use this to 'copy' an ARC/INFO coverage or other feature data source into a shapefile that you can edit, or to copy a selected subset of features into a shapefile.

Merge Themes button

You can merge 2 or more themes together if they are made up of the same feature type (polygon OR line OR point). The Merge button operates on all the selected features (or all the features if none are selected) of all the active themes in the View. The first active theme's table structure will be kept, and if the other active themes have columns with the same names, the attributes from those columns will be transferred to the new theme; if not, the attributes will be lost. At the end, you will be informed how many features from each active theme were merged into the new shapefile. Before merging, carefully check that the features you want from each theme are selected, or if you want all the features, make sure that none are selected by clicking the ArcView Clear Selected Features button.

One instance where you might use this function is when you want to edit only a small portion of a large polygon theme. This may be necessary for large themes, because the Build function can be very slow for large quantities of data. You can select the polygons in the area of the theme you wish to edit (make sure that your edits won't affect the common boundaries with any polygons you don't select to edit--one way to make sure this doesn't happen is to select discrete clumps of polygons to edit--say, a bunch of polygons that form an island separate from the rest) and unbuild those polygons into polylines and labelpoints using the Unbuild Theme button on the Main Menu. Then, edit the lines as needed using the Parcel Editor and build them back into polygons using the Build Theme button (on either the Parcel Editor or the Main Menu), making sure you incorporate the attributes from the labelpoints you made. Make sure none of these new polygons are selected. Then, 'swap' the selection on your original polygon theme (select all the polygons that weren't selected and unselect all the polygons that were selected (the ones that got unbuilt)). There is a Swap selection function on the Main Menu--just click the Additional Options button. Another way to swap the selection is to make the theme active, click the Open Theme Table button on the View button bar, and while the table is the active document click the Switch Selection button on the Table button bar.

Next, make both the newly built polygon theme (with no features selected) and the original polygon theme (with all the other features selected) active, and click the Merge button. In this case, it won't matter which theme is the first active theme since they both have the same table structure. An alternative to Merge is to use the Put features from themes into editable theme function from the Additional Options button to transfer features from one theme to another.

The merge function is based on an ArcView sample script, MergeThemesClick, with slight modifications.

previous topic   |   home   |   next topic

This document was created by DEM/ NWF. Contact: DEM/ NWF.