Hi, the "no-data" pixels are, presumably, because you have your slope raster in degrees, convert it to radians. There is actually a ready script awailable: LSscript for ArcGIS by van Remortel v30-09-11.zip just Google it. You might also find it useful to check the following articles out:
Boehner, J., Selige, T. (2006):
Spatial Prediction of Soil Attributes Using Terrain Analysis and Climate Regionalisation'
In: Boehner, J., McCloy, K.R., Strobl, J.: 'SAGA �?? Analysis and Modelling Applications', Goettinger Geographische Abhandlungen, Vol.115, p.13-27
Desmet & Govers (1996):
'A GIS Procedure for Automatically Calculating the USLE LS Factor on Topographically Complex Landscape Units'
Journal of Soil and Water Conservation, 51(5):427.433
Kinnell, P.I.A. (2005):
'Alternative Approaches for Determining the USLE-M Slope Length Factor for Grid Cells.'
Moore, I.D., Grayson, R.B., Ladson, A.R. (1991):
'Digital terrain modelling: a review of hydrogical, geomorphological, and biological applications'
Hydrological Processes, Vol.5, No.1
And I don't want to scare you:)))), but there is a whole bunch of different algorithms of LS-factor calculation out there, they produce the same data distribution, but absolute values are up to 4-5 times different %), check out which works best for your terrain. And the last but the most important, no offence to ESRI and ArcGIS, but check SAGA GIS out, it's free and open, runs both in Windows and Linux and has already many of such functions (LS-factor calculation as well) built in, that can be with just a couple of clicks right from DEM calculated.
Good Luck!
