I am working on stream network delineation with GRASS 7 in RQGIS, the 'r.stream.extract' algorithm in particular. However, the algorithm returns erroneous result when the Advanced parameter, "v.out.ogr output type" has not been defined as "line". The advanced parameters setting is accessible in the QGIS GUI ver 2.14.17 (as shown below)

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but couldn't be found as argument in RQGIS.

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I wonder if there is anything that I have missed. Is there any workaround to solve this?

  • Try setting GRASS_OUTPUT_TYPE_PARAMETER as 2. The options from the GUI are seen as index values: auto = 0; point = 1; line = 2; and area = 3.
    – Joseph
    Aug 14, 2017 at 11:57
  • Nice one! Glad you got it working :)
    – Joseph
    Aug 28, 2017 at 9:01

1 Answer 1


Joseph has already told you the correct answer. But just to make it clear. To find out about possible values for a specific parameter, run get_usage(). In your case run:


This results in:

ALGORITHM: r.stream.extract - Stream network extraction
elevation <ParameterRaster>
  accumulation <ParameterRaster>
  depression <ParameterRaster>
  threshold <ParameterNumber>
  mexp <ParameterNumber>
  stream_length <ParameterNumber>
  d8cut <ParameterNumber>
  stream_raster <OutputRaster>
  stream_vector <OutputVector>
  direction <OutputRaster>

GRASS_OUTPUT_TYPE_PARAMETER(v.out.ogr output type)
0 - auto
1 - point
2 - line
3 - area

So setting GRASS_OUTPUT_TYPE_PARAMETER to 2 ("line" should also work), as pointed out by Joseph, should do what you want.

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