org.renjin.eval.EvalException：找不到带有Renjin标签数据的对象'a'

Question

我正在尝试从Java构建R的data.frame。当填充int / double值时，它将转换为R中的data.frame，但是当我尝试使用标签数据时，它将抛出未找到对象的异常。

    public static void main(String[] args) throws ScriptException, FileNotFoundException {
                RenjinScriptEngineFactory factory = new RenjinScriptEngineFactory();
                ScriptEngine engine = factory.getScriptEngine();
                engine.eval("source(\"script.R\")");
                engine.eval("workflow.predict("+getData()+")");
            }

            public static ListVector getData() {
                StringArrayVector.Builder userid = new StringArrayVector.Builder();
                StringArrayVector.Builder defaultCC = new StringArrayVector.Builder();
                StringArrayVector.Builder expenseTypeId = new StringArrayVector.Builder();
                StringArrayVector.Builder amount = new StringArrayVector.Builder();
                StringArrayVector.Builder cc = new StringArrayVector.Builder();
                StringArrayVector.Builder activity = new StringArrayVector.Builder();

                userid.add("62020");
                defaultCC.add("3141877");
                expenseTypeId.add("46013");
                amount.add("1000");
                cc.add("3141877");
                activity.add("72004");

                userid.add("62020");
                defaultCC.add("3141877");
                expenseTypeId.add("46013");
                amount.add("1001");
                cc.add("3141877");
                activity.add("72001");

                ListVector.NamedBuilder myDf = new ListVector.NamedBuilder();
                myDf.setAttribute(Symbols.CLASS, StringVector.valueOf("data.frame"));
                myDf.setAttribute(Symbols.ROW_NAMES, new RowNamesVector(2)); 
                myDf.add("userid", userid.build());
                myDf.add("defaultCC", defaultCC.build());
                myDf.add("expenseTypeId", expenseTypeId.build());
                myDf.add("amount", amount.build());
                myDf.add("cc", cc.build());
                myDf.add("activity", activity.build());
                return myDf.build();
            }



script.R


workflow.predict <- function(abc) {
    print(data.frame(lapply(abc, as.character), stringsAsFactors=FALSE))
    dataset = data.frame(lapply(abc, as.character), stringsAsFactors=FALSE)
    library(randomForest)
    classifier = randomForest(x = dataset[-6], y = as.factor(dataset$activity))
    # Predicting the Test set results
    new.data=c(62020,3141877,46013,950,3141877)
    y_pred = predict(classifier, newdata = new.data)
    print(y_pred)
    return(y_pred)
}

但是当我尝试使用标签数据时，它会抛出错误以下消息。

Code

    userid.add("a");


Exception in thread "main" org.renjin.eval.EvalException: object 'a' not found
    at org.renjin.eval.Context.evaluateSymbol(Context.java:335)
    at org.renjin.eval.Context.evaluate(Context.java:278)
    at org.renjin.eval.Context.evaluate(Context.java:264)