[R-sig-Geo] Problem with gain/offset and sampleRegular

[Ned Horning]

Hi - I am working on a topographic correction script and am having a 
problem with the gain and offset settings.

This is how I set the gain and offset:
gainVal <- 0.108078
offsetVal <- -0.37
gain(satImage) <- gainVal
offs(satImage) <- offsetVal

When I look at the gain/offset values they look fine:
 > gain(satImage)
[1] 0.108078
 > offs(satImage)
[1] -0.37

When I get a bunch of samples using sampleRegular (or sampleRandom) the 
retrieved values are not correct:
 > satImageSamps <- sampleRegular(satImage, numSamps, cells=TRUE)
 > head(satImageSamps)
      cell p125r49_5t19890217_subset
[1,] 1504                0.41935178
[2,] 1511                0.48943690
[3,] 1518                0.51279861
[4,] 1525                0.40767093
[5,] 1532                0.06892616
[6,] 1539                0.30254324

But if I extract the value for the first cell in satImageSamps the value 
looks like what I would expect:
 > extract(satImage, 1504)
6.871226

If I run the script without altering the gain and offset values I still 
get different values for the same cell number using sampleRegular and 
extract but they are roughly the same. I have a similar problem using 
sampleRandom - the value returned for a cell is different than what I 
get using extract with the cell number.

Is this a bug or am I doing something wrong?

I am using raster version 1.9-19 downloaded from the CRAN.

All the best,

Ned