If you have designed a language engine, you may call this function in the end to format and return the text output from your engine.
engine_output(options, code, out, extra = NULL)a list of chunk options (usually this is just the object
options passed to the engine function; see
knit_engines)
the source code of the chunk, to which the output hook
source is applied, unless the chunk option echo == FALSE
the text output from the engine, to which the hook output
is applied, unless the chunk option results == 'hide'
any additional text output that you want to include
A character string generated from the source code and output using the appropriate output hooks.