[R-sig-Geo] proper syntax for passing MINUSERPIXELVALUE, MAXUSERPIXELVALUE to Terragen driver

[Chris English]

Dear List,
I have a SpatialGridDataFrame that from which I hope to createa Terragen file.
My consistent error in create2GDAL:
GDAL Error 1: Inverted, flat, or unspecified span for Terragen file.
I need to pass the options =c("MINUSERPIXELVALUE = 1", "MAXUSERPIXELVALUE=2736")to the Terragen driver and don't know how.
Details of writeGDAL suggest:it may also be necessary in some cases to escape quotation markes if included in thestring passed to the driver.
As there aren't embedded quotation marks, I don't think this applies.  But, ifone doesn't establish the MIN/MAX~USERPIXELVALUE, one will always get the aboveerror.
Thank you,
Chris English