When you select the training data segments, ENVI is storing the location where you selected and not the actual polygon. If you want all the polygons, you can save the segmentation image. From the ENVI Help on Example-Based Classification: To save your training data for all classes to a point shapefile, click the Save Example File button. ENVI saves the pixel coordinates of the points where you clicked when selecting training regions, along with map coordinates if the image is georeferenced.

Thank you for the response. The segmentation file contains whole segments which I do not want . I am interested to perform some statistical analysis of the ROIs.But as per your view, if it saves only the point ( where I have clicked) while selecting the examples, I am now more surprised what is the meaning of Min, Max, avg, std deviation, length and other attributes that we get. I suppose that they should represent the polygon that we have selected while creating the examples. Still I am not clear. Could you explain further.

The segmentation image contains all of the attributes which are calculated on the segment polygons, not a point. If you only wish to have some of the polygon segments, then you could export the segmentation image to a shapefile and subset it by the regions you are interested in using vector tools or in ArcGIS. There are no ROIs that are created in the Example based classification.

Thank you for the answer. Well, now this loops back to my original question again. This calculates the statistics for polygon- its natural and expected. But what surprised me was the shape to be "point" rather than "polygon" when I open the attribute table of this shape file (example.shp). That was what I wanted to be clear on.Thanks,