Generate new dataframe with Execute R

Hi,

I am new to RM and tried to use Execute R to apply KS-test and return its result, which is a dataframe. When I ran my process, it shows "Process failed. Script terminated abnormally":

• Exception: com.rapidminer.operator.OperatorException
• Message: Script terminated abnormally.
• Stack trace:
• com.rapidminer.extension.rscripting.operator.scripting.AbstractScriptRunner.run(AbstractScriptRunner.java:166)
• com.rapidminer.extension.rscripting.operator.scripting.AbstractScriptingLanguageOperator.doWork(AbstractScriptingLanguageOperator.java:90)
• com.rapidminer.extension.rscripting.operator.scripting.r.RScriptingOperator.doWork(RScriptingOperator.java:73)
• com.rapidminer.operator.Operator.execute(Operator.java:1004)
• com.rapidminer.operator.execution.SimpleUnitExecutor.execute(SimpleUnitExecutor.java:77)
• com.rapidminer.operator.ExecutionUnit$3.run(ExecutionUnit.java:812)
• com.rapidminer.operator.ExecutionUnit$3.run(ExecutionUnit.java:807)
• java.security.AccessController.doPrivileged(Native Method)
• com.rapidminer.operator.ExecutionUnit.execute(ExecutionUnit.java:807)
• com.rapidminer.operator.OperatorChain.doWork(OperatorChain.java:428)
• com.rapidminer.operator.Operator.execute(Operator.java:1004)
• com.rapidminer.Process.execute(Process.java:1310)
• com.rapidminer.Process.run(Process.java:1285)
• com.rapidminer.Process.run(Process.java:1176)
• com.rapidminer.Process.run(Process.java:1129)
• com.rapidminer.Process.run(Process.java:1124)
• com.rapidminer.Process.run(Process.java:1114)
• com.rapidminer.gui.ProcessThread.run(ProcessThread.java:65)

I can run the example code without similar problem and if I deleted the last two lines - "ks.table<-as.data.table(ks.table)
return(ks.table)". It is fine as well...

Here is my XML.:

<?xml version="1.0" encoding="UTF-8"?><process version="8.1.000">
  <context>
    <input/>
    <output/>
    <macros/>
  </context>
  <operator activated="true" class="process" compatibility="8.1.000" expanded="true" name="Process">
    <process expanded="true">
      <operator activated="true" class="retrieve" compatibility="8.1.000" expanded="true" height="68" name="Retrieve Golf" width="90" x="45" y="34">
        <parameter key="repository_entry" value="//Samples/data/Golf"/>
      </operator>
      <operator activated="true" class="r_scripting:execute_r" compatibility="8.1.000" expanded="true" height="82" name="Execute R (2)" width="90" x="246" y="34">
        <parameter key="script" value="# rm_main is a mandatory function, &#10;# the number of arguments has to be the number of input ports (can be none)&#10;rm_main = function(data)&#10;{&#10;library(dplyr)&#10;library(data.table)&#10;&#10;columnname&lt;-c()&#10;&#10;###Save the column name and label name:&#10;for(i in seq(along = metaData$data)){&#10;&#9;columnname&lt;-c(columnname, names(metaData$data)[i])&#10;&#9;&#10;&#9;if (metaData$data[[i]]$role == 'label'){&#10;&#9;labelname&lt;- names(metaData$data)[i]&#10;&#9;}&#10;}&#10;&#10;### apply filter based on the label:&#10;expyes&lt;-lazyeval::interp(quote(x == y), x=as.name(labelname), y = &quot;yes&quot;)&#10;expno&lt;-lazyeval::interp(quote(x == y), x=as.name(labelname), y = &quot;no&quot;)&#10;&#10;yes&lt;- filter_(data, expyes)&#10;no&lt;- filter_(data, expno)&#10;&#10;ks.table&lt;-data.frame()&#10;&#10;for(i in seq(along = metaData$data)){&#10;&#9;if ((metaData$data[[i]]$role == 'label') | (metaData$data[[i]]$type != &quot;Integer&quot;) ) next&#10;&#9;&#10;&#9;cyes&lt;-select(yes, select = names(metaData$data)[i])&#10;&#9;cno&lt;- select(no, select = names(metaData$data)[i])&#10;&#9;ks&lt;-ks.test(cyes, cno)&#10;&#9;row&lt;-data.frame(names(metaData$data)[i], ks$statistic,ks$p.value)&#10;&#9;print(as.character(row))&#10;&#9;ks.table&lt;-rbind(ks.table, row)&#10;}&#10;ks.table&lt;-as.data.table(ks.table)&#10;return(ks.table)&#10;}&#10;"/>
      </operator>
      <connect from_op="Retrieve Golf" from_port="output" to_op="Execute R (2)" to_port="input 1"/>
      <connect from_op="Execute R (2)" from_port="output 1" to_port="result 1"/>
      <portSpacing port="source_input 1" spacing="0"/>
      <portSpacing port="source_input 2" spacing="0"/>
      <portSpacing port="sink_result 1" spacing="0"/>
      <portSpacing port="sink_result 2" spacing="0"/>
    </process>
  </operator>
</process>

Does anyone have idea why it happens? Thanks for help!