Cross-Validation of R model failed

Hi RapidMiner,

I followed this tutorial (http://community.rapidminer.com/t5/RapidMiner-Studio-Knowledge-Base/Cross-Validation-of-R-Python-Models/ta-p/31978) to do cross validation of R Random Forest regression model but encountered an error as in the attached photo. However, the same R scripts work well for the single validation as in the attached process (Single-Validation.rmp). I also attached the cross validation process here. Do you have any idea?

Thanks a lot!

Best Regards,

phivu