I am trying to run my QGIS model inside R using the qgisprocess package.
The model gets a raster and vector line inputs. Its output is an attribute-only QGIS table.

Here is the model diagram in QGIS

Here is the code I am using in R:

library(qgisprocess)
library(sf)
library(terra)

# load data
elevation <- rast(DEM_RW_UTM36S.tif"))
route <- st_read("Distances.gpkg", layer = "lines")

# run the model
result <- qgis_run_algorithm(
    algorithm = "model:Route_slope_assessment",
    dem = elevation,
    route = route,
    .quiet = FALSE
)

I am getting an error with the message:

ERROR: The following mandatory parameters were not specified

slopes: slopes

My issue is that when I add the slopes parameter as indicated in this message and supply it with a path to a csv file to create, then I get an error that that the supplied “slopes” argument is unused.

I have verified that this algorithm is available in qgisprocess.
Using qgis_show_help("model:Route_slope_assessment") shows that the model expects an additional parameter called route_slope_analysis of type sink. I don’t know what this argument is or how to specify it.

What is the proper way to specify this model output and read it back into R as a dataframe?