How to exlude raster cell from the cost surface estimation?

[RobertoFilloramo]

I use ArcGIS 10.1, I am trying to generate a cost surface (Path Distance tool) in order to generate a least-cost path. The problem is that I would exclude a specific area of the raster from the calculation. I tried to remove it with the tool Clip, but it didn't work (it took away the interested raster portion leaving just the useless one). Do you have a suggestion?

[DanPatterson_Retired · Accepted solution]

Don't know if 10.1 has 

Erase—Help | ArcGIS Desktop 

It would require the spatial analyst extension for that version in any event.

Alternatively, you could mask the area with null values using

con and setnull

Setting values to NoData with Set Null—Help | ArcGIS Desktop 

nodata cells are excluded from raster analyses

[RobertoFilloramo]

Thank you for your answer... I tried with Con and Set Null tools, firstly I converted my polygon to raster (setting for the extent and the snap the slope), then I use Map Algebra using the expression "Con (IsNull (polytoraster), slope, 0)" (output Slope_Con) and afterwards I used the new raster in the SetNull tool setting as input conditional raster "Slope_Con", expression "value=0" and input false raster or constant value "Slope_Con".
The result was what I wanted.