fixes #1420

man/terrain.Rd

@@ -43,9 +43,9 @@ If two cells have the same drop in elevation, a random cell is picked. That is n
 
 Most terrain indices are according to Wilson et al. (2007), as in \href{https://gdal.org/programs/gdaldem.html}{gdaldem}. TRI (Terrain Ruggedness Index) is the mean of the absolute differences between the value of a cell and its 8 surrounding cells. TPI (Topographic Position Index) is the difference between the value of a cell and the mean value of its 8 surrounding cells. Roughness is the difference between the maximum and the minimum value of a cell and its 8 surrounding cells. 
 
-TRIriley (TRI according to Riley et al. (2007)) returns the square root of summed squared differences between the value of a cell and its 8 surrounding cells. TRIrmsd computes the square root of the mean of the squared differences between these cells. The benefit of  TRIrmsd
+TRIriley (TRI according to Riley et al., 2007) returns the square root of summed squared differences between the value of a cell and its 8 surrounding cells. TRIrmsd computes the square root of the mean of the squared differences between these cells. 
 
-Such measures can also be computed with the \code{\link{focal}} function:
+These measures can also be computed with \code{\link{focal}} functions:
 
 TRI <- focal(x, w=3, fun=\(x) sum(abs(x[-5]-x[5]))/8)