I have a problem to mask the the raster which has values ranges -0.73106217384338 - 0.94593381881714. These values have been derived by using equatin (B3-B4)/(B3+B4) from Landsat band 3 and band 4 spectral reflectance values in arcgis 10. Raster image was of 32 bit tif file formate. I applied the function Extract by mask in arcgis with input this raster and polygon shape file as feature mask. But polygon that i used here cover some more area than the raster. The output raster have some real values like 0.435936 here for the areas where there is no raster beneath the polygon.
How can i get rid of this value using ArcGIS 10?