Question

我有一条sklearn管道。其步骤之一是 ExpressionTransformer(f"round(X[0]*{nRoundMin})/{nRoundMin}")（从sklearn2pmml.preprocessing导入ExpressionTransformer）。当我尝试将此管道写入PMML文件时，出现以下错误：

Standard output is empty
Standard error:
Jun 27, 2019 8:39:55 AM org.jpmml.sklearn.Main run
INFO: Parsing PKL..
Jun 27, 2019 8:40:53 AM org.jpmml.sklearn.Main run
INFO: Parsed PKL in 58085 ms.
Jun 27, 2019 8:40:53 AM org.jpmml.sklearn.Main run
INFO: Converting..
Jun 27, 2019 8:41:03 AM org.jpmml.sklearn.Main run
SEVERE: Failed to convert
java.lang.IllegalArgumentException: round
    at org.jpmml.sklearn.ExpressionTranslator.translateFunction(ExpressionTranslator.java:94)
    at org.jpmml.sklearn.ExpressionTranslator.FunctionInvocationExpression(ExpressionTranslator.java:513)
    at org.jpmml.sklearn.ExpressionTranslator.PrimaryExpression(ExpressionTranslator.java:416)
    at org.jpmml.sklearn.ExpressionTranslator.UnaryExpression(ExpressionTranslator.java:374)
    at org.jpmml.sklearn.ExpressionTranslator.MultiplicativeExpression(ExpressionTranslator.java:316)
    at org.jpmml.sklearn.ExpressionTranslator.AdditiveExpression(ExpressionTranslator.java:280)
    at org.jpmml.sklearn.ExpressionTranslator.ComparisonExpression(ExpressionTranslator.java:228)
    at org.jpmml.sklearn.ExpressionTranslator.NegationExpression(ExpressionTranslator.java:217)
    at org.jpmml.sklearn.ExpressionTranslator.LogicalAndExpression(ExpressionTranslator.java:187)
    at org.jpmml.sklearn.ExpressionTranslator.LogicalOrExpression(ExpressionTranslator.java:166)
    at org.jpmml.sklearn.ExpressionTranslator.IfElseExpression(ExpressionTranslator.java:147)
    at org.jpmml.sklearn.ExpressionTranslator.Expression(ExpressionTranslator.java:140)
    at org.jpmml.sklearn.ExpressionTranslator.translateExpressionInternal(ExpressionTranslator.java:134)
    at org.jpmml.sklearn.ExpressionTranslator.translate(ExpressionTranslator.java:33)
    at org.jpmml.sklearn.ExpressionTranslator.translate(ExpressionTranslator.java:22)
    at sklearn2pmml.preprocessing.ExpressionTransformer.encodeFeatures(ExpressionTransformer.java:43)
    at sklearn.pipeline.Pipeline.encodeFeatures(Pipeline.java:81)

尽管round在PMML内置函数（http://dmg.org/pmml/v4-2-1/BuiltinFunctions.html#math）中。我应该如何编写此流水线步骤来正确获取round函数？

如果我在上面的ExpressionTransfomer中删除了round函数，则创建PMML不会出现任何问题。

我还尝试将上述ExpressionTransfomer替换为

Pipeline([
    ("i", ExpressionTransformer("X[0]*"+str(nRoundMin))),
    ("r", FunctionTransformer(np.round)),
    ("f", ExpressionTransformer("X[0]/"+str(nRoundMin)))
])

和

Pipeline([
    ("i", ExpressionTransformer("X[0]*"+str(nRoundMin))),
    ("r", FunctionTransformer(round)),
    ("f", ExpressionTransformer("X[0]/"+str(nRoundMin)))
])

但这没有帮助。

[编辑] 按照user1808924的建议，我还尝试了ExpressionTransformer(f"numpy.rint(X[0]*{nRoundMin})/{nRoundMin}")，它产生了类似的错误：

Standard output is empty
Standard error:
Jun 27, 2019 12:38:51 PM org.jpmml.sklearn.Main run
INFO: Parsing PKL..
Jun 27, 2019 12:39:54 PM org.jpmml.sklearn.Main run
INFO: Parsed PKL in 63076 ms.
Jun 27, 2019 12:39:54 PM org.jpmml.sklearn.Main run
INFO: Converting..
Jun 27, 2019 12:40:05 PM org.jpmml.sklearn.Main run
SEVERE: Failed to convert
java.lang.IllegalArgumentException: numpy.rint
    at org.jpmml.sklearn.ExpressionTranslator.translateFunction(ExpressionTranslator.java:94)
    at org.jpmml.sklearn.ExpressionTranslator.FunctionInvocationExpression(ExpressionTranslator.java:513)
    at org.jpmml.sklearn.ExpressionTranslator.PrimaryExpression(ExpressionTranslator.java:416)
    at org.jpmml.sklearn.ExpressionTranslator.UnaryExpression(ExpressionTranslator.java:374)
    at org.jpmml.sklearn.ExpressionTranslator.MultiplicativeExpression(ExpressionTranslator.java:316)
    at org.jpmml.sklearn.ExpressionTranslator.AdditiveExpression(ExpressionTranslator.java:280)
    at org.jpmml.sklearn.ExpressionTranslator.ComparisonExpression(ExpressionTranslator.java:228)
    at org.jpmml.sklearn.ExpressionTranslator.NegationExpression(ExpressionTranslator.java:217)
    at org.jpmml.sklearn.ExpressionTranslator.LogicalAndExpression(ExpressionTranslator.java:187)
    at org.jpmml.sklearn.ExpressionTranslator.LogicalOrExpression(ExpressionTranslator.java:166)
    at org.jpmml.sklearn.ExpressionTranslator.IfElseExpression(ExpressionTranslator.java:147)
    at org.jpmml.sklearn.ExpressionTranslator.Expression(ExpressionTranslator.java:140)
    at org.jpmml.sklearn.ExpressionTranslator.translateExpressionInternal(ExpressionTranslator.java:134)
    at org.jpmml.sklearn.ExpressionTranslator.translate(ExpressionTranslator.java:33)
    at org.jpmml.sklearn.ExpressionTranslator.translate(ExpressionTranslator.java:22)
    at sklearn2pmml.preprocessing.ExpressionTransformer.encodeFeatures(ExpressionTransformer.java:43)

Answer 1

ExpressionTransformer期望一个字符串参数，该字符串参数是有效的Python表达式（可在本地工作空间环境中评估）。因此，如果要应用舍入，则需要使用一些内置的Python函数。

例如，您可以使用Numpy's rint universal function：

transformer = ExpressionTransformer("numpy.rint(X[0] / X[1])")

如何将Round函数从python转换为PMML？

1 个答案: