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Diffstat (limited to 'docs/sparkr.md')
| -rw-r--r-- | docs/sparkr.md | 107 |
1 files changed, 53 insertions, 54 deletions
diff --git a/docs/sparkr.md b/docs/sparkr.md index dfa5278ef8..4bbc362c52 100644 --- a/docs/sparkr.md +++ b/docs/sparkr.md @@ -322,8 +322,59 @@ head(ldf, 3) Apply a function to each group of a `SparkDataFrame`. The function is to be applied to each group of the `SparkDataFrame` and should have only two parameters: grouping key and R `data.frame` corresponding to that key. The groups are chosen from `SparkDataFrame`s column(s). The output of function should be a `data.frame`. Schema specifies the row format of the resulting -`SparkDataFrame`. It must represent R function's output schema on the basis of Spark data types. The column names of the returned `data.frame` are set by user. Below is the data type mapping between R -and Spark. +`SparkDataFrame`. It must represent R function's output schema on the basis of Spark [data types](#data-type-mapping-between-r-and-spark). The column names of the returned `data.frame` are set by user. + +<div data-lang="r" markdown="1"> +{% highlight r %} + +# Determine six waiting times with the largest eruption time in minutes. +schema <- structType(structField("waiting", "double"), structField("max_eruption", "double")) +result <- gapply( + df, + "waiting", + function(key, x) { + y <- data.frame(key, max(x$eruptions)) + }, + schema) +head(collect(arrange(result, "max_eruption", decreasing = TRUE))) + +## waiting max_eruption +##1 64 5.100 +##2 69 5.067 +##3 71 5.033 +##4 87 5.000 +##5 63 4.933 +##6 89 4.900 +{% endhighlight %} +</div> + +##### gapplyCollect +Like `gapply`, applies a function to each partition of a `SparkDataFrame` and collect the result back to R data.frame. The output of the function should be a `data.frame`. But, the schema is not required to be passed. Note that `gapplyCollect` can fail if the output of UDF run on all the partition cannot be pulled to the driver and fit in driver memory. + +<div data-lang="r" markdown="1"> +{% highlight r %} + +# Determine six waiting times with the largest eruption time in minutes. +result <- gapplyCollect( + df, + "waiting", + function(key, x) { + y <- data.frame(key, max(x$eruptions)) + colnames(y) <- c("waiting", "max_eruption") + y + }) +head(result[order(result$max_eruption, decreasing = TRUE), ]) + +## waiting max_eruption +##1 64 5.100 +##2 69 5.067 +##3 71 5.033 +##4 87 5.000 +##5 63 4.933 +##6 89 4.900 + +{% endhighlight %} +</div> #### Data type mapping between R and Spark <table class="table"> @@ -394,58 +445,6 @@ and Spark. </tr> </table> -<div data-lang="r" markdown="1"> -{% highlight r %} - -# Determine six waiting times with the largest eruption time in minutes. -schema <- structType(structField("waiting", "double"), structField("max_eruption", "double")) -result <- gapply( - df, - "waiting", - function(key, x) { - y <- data.frame(key, max(x$eruptions)) - }, - schema) -head(collect(arrange(result, "max_eruption", decreasing = TRUE))) - -## waiting max_eruption -##1 64 5.100 -##2 69 5.067 -##3 71 5.033 -##4 87 5.000 -##5 63 4.933 -##6 89 4.900 -{% endhighlight %} -</div> - -##### gapplyCollect -Like `gapply`, applies a function to each partition of a `SparkDataFrame` and collect the result back to R data.frame. The output of the function should be a `data.frame`. But, the schema is not required to be passed. Note that `gapplyCollect` can fail if the output of UDF run on all the partition cannot be pulled to the driver and fit in driver memory. - -<div data-lang="r" markdown="1"> -{% highlight r %} - -# Determine six waiting times with the largest eruption time in minutes. -result <- gapplyCollect( - df, - "waiting", - function(key, x) { - y <- data.frame(key, max(x$eruptions)) - colnames(y) <- c("waiting", "max_eruption") - y - }) -head(result[order(result$max_eruption, decreasing = TRUE), ]) - -## waiting max_eruption -##1 64 5.100 -##2 69 5.067 -##3 71 5.033 -##4 87 5.000 -##5 63 4.933 -##6 89 4.900 - -{% endhighlight %} -</div> - #### Run local R functions distributed using `spark.lapply` ##### spark.lapply |