In the earlier examples the input from usql was a single data frame stored in inputFromUSQL. In this example we will pass two inputs from usql and store it in two data frames - rightFromUSQL and leftFromUSQL. This ability to use R scripts as combiners(two inputs) is targeted for scoring scenario. You can now train using the reducer and score test/validation data using the generated models with the combiner.
usqlscriptEx8a.usql we send two inputs to the R script and output a subset of combined data.
usqlscriptEx8b.usql we send two inputs to the R script - the trained model and the data to score and output the predictions and the scoring data.
More on COMBINE Expression (U-SQL).