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https://issues.apache.org/jira/browse/SPARK-18569?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15748440#comment-15748440
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Yanbo Liang edited comment on SPARK-18569 at 12/14/16 2:26 PM:
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This is generally a good idea, but I think we need to delimit the scope of
these functions to set priority, which functions are the most popular used for
R users? If we figure out the route for the first arithmetic function, we can
add others simple and reproducible. To archive this, it's better we can have a
basic design document for {{RFormula}} improvement, to make this architecture
scalable and maintainable.
Actually we have used a tricky way when implementing {{spark.survreg}}, since
it requires R formula likes Surv(futime, fustat) ~ ecog_ps + rx which has two
elements in the label/response side and need to support {{Surv}} as keyword,
but {{RFormula}} does not support them currently. We can put these issues
together to figure out an elegant way.
was (Author: yanboliang):
This is generally a good idea, but I think we need to delimit the scope of
these functions to set priority, which functions are the most popular used for
R users? If we figure out the route for the first arithmetic function, we can
add others simple and reproducible. To archive this, it's better we can have a
basic design document for {{RFormula}} improvement, to make this architecture
scalable and maintainable.
Actually we have used a tricky way when implementing {{spark.survreg}}, since
it requires R formula likes Surv(futime, fustat) ~ ecog_ps + rx which has two
elements in the label/response side and need to support {{Surv}} as keyword,
but {{RFormula}} does not support them currently. We can put this issues
together to figure out an elegant way.
> Support R formula arithmetic
> -----------------------------
>
> Key: SPARK-18569
> URL: https://issues.apache.org/jira/browse/SPARK-18569
> Project: Spark
> Issue Type: Sub-task
> Components: ML, SparkR
> Reporter: Felix Cheung
>
> I think we should support arithmetic which makes it a lot more convenient to
> build model. Something like
> {code}
> log(y) ~ a + log(x)
> {code}
> And to avoid resolution confusions we should support the I() operator:
> {code}
> I
> I(X∗Z) as is: include a new variable consisting of these variables multiplied
> {code}
> Such that this works:
> {code}
> y ~ a + I(b+c)
> {code}
> the term b+c is to be interpreted as the sum of b and c.
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