[SPARK-19395][SparkR]Convert coefficients in summary to matrix

[actuaryzhang]

What changes were proposed in this pull request?

The coefficients component in model summary should be 'matrix' but the underlying structure is indeed list. This affects several models except for 'AFTSurvivalRegressionModel' which has the correct implementation. The fix is to first unlist the coefficients returned from the callJMethod before converting to matrix. An example illustrates the issues:

data(iris)
df <- createDataFrame(iris)
model <- spark.glm(df, Sepal_Length ~ Sepal_Width, family = "gaussian")
s <- summary(model)

> str(s$coefficients)
List of 8
 $ : num 6.53
 $ : num -0.223
 $ : num 0.479
 $ : num 0.155
 $ : num 13.6
 $ : num -1.44
 $ : num 0
 $ : num 0.152
 - attr(*, "dim")= int [1:2] 2 4
 - attr(*, "dimnames")=List of 2
  ..$ : chr [1:2] "(Intercept)" "Sepal_Width"
  ..$ : chr [1:4] "Estimate" "Std. Error" "t value" "Pr(>|t|)"
> s$coefficients[, 2]
$`(Intercept)`
[1] 0.4788963

$Sepal_Width
[1] 0.1550809

This shows that the underlying structure of coefficients is still list.

@felixcheung @wangmiao1981

[SparkQA]

Test build #72113 has finished for PR 16730 at commit c80d530.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[felixcheung]

@actuaryzhang since this changes the output, could you open a JIRA for this?

[felixcheung]

thanks, i'd be great if you could add some tests for this - perhaps just to check the correct type and/or a subset of values

[actuaryzhang]

@felixcheung I created a JIRA ticket and added in some tests. Please take a look. Thanks.

[SparkQA]

Test build #72129 has finished for PR 16730 at commit 7ded346.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[felixcheung]

merged to master, thanks!