sparkR could not find function "textFile"

Yeah, that’s probably because the head() you’re invoking there is defined for SparkR DataFrames
[1] (note how you don’t have to use the SparkR::: namepsace in front of it), but SparkR:::textFile()
returns an RDD object, which is more like a distributed list data structure the way you’re
applying it over that .md text file. If you want to look at the first item or first several
items in the RDD, I think you want to use SparkR:::first() or SparkR:::take(), both of which
are applied to RDDs.


Just remember that all the functions described in the public API [2] for SparkR right now
are related mostly to working with DataFrames. You’ll have to use the R command line doc
or look at the RDD source code for all the private functions you might want (which includes
the doc strings used to make the R doc), whichever you find easier.


Alek


[1] -- http://spark.apache.org/docs/latest/api/R/head.html
[2] -- https://spark.apache.org/docs/latest/api/R/index.html
[3] -- https://github.com/apache/spark/blob/master/R/pkg/R/RDD.R


From: Wei Zhou >
Date: Thursday, June 25, 2015 at 3:49 PM
To: Aleksander Eskilson >
Cc: "[email protected]" >
Subject: Re: sparkR could not find function "textFile"


Hi Alek,


Just a follow up question. This is what I did in sparkR shell:


lines <- SparkR:::textFile(sc, "./README.md")
head(lines)


And I am getting error:


"Error in x[seq_len(n)] : object of type 'S4' is not subsettable"


I'm wondering what did I do wrong. Thanks in advance.


Wei


2015-06-25 13:44 GMT-07:00 Wei Zhou >:
Hi Alek,


Thanks for the explanation, it is very helpful.


Cheers,
Wei


2015-06-25 13:40 GMT-07:00 Eskilson,Aleksander >:
Hi there,


The tutorial you’re reading there was written before the merge of SparkR for Spark 1.4.0
For the merge, the RDD API (which includes the textFile() function) was made private, as the
devs felt many of its functions were too low level. They focused instead on finishing the
DataFrame API which supports local, HDFS, and Hive/HBase file reads. In the meantime, the
devs are trying to determine which functions of the RDD API, if any, should be made public
again. You can see the rationale behind this decision on the issue’s JIRA [1].


You can still make use of those now private RDD functions by prepending the function call
with the SparkR private namespace, for example, you’d use
SparkR:::textFile(…).


Hope that helps,
Alek


[1] -- https://issues.apache.org/jira/browse/SPARK-7230


From: Wei Zhou >
Date: Thursday, June 25, 2015 at 3:33 PM
To: "[email protected]" >
Subject: sparkR could not find function "textFile"


Hi all,


I am exploring sparkR by activating the shell and following the tutorial here https://amplab-extras.github.io/SparkR-pkg/


And when I tried to read in a local file with textFile(sc, "file_location"), it gives an error
could not find function "textFile".


By reading through sparkR doc for 1.4, it seems that we need sqlContext to import data, for
example.


people <- read.df(sqlContext, "./examples/src/main/resources/people.json", "json"


)
And we need to specify the file type.


My question is does sparkR stop supporting general type file importing? If not, would appreciate
any help on how to do this.


PS, I am trying to recreate the word count example in sparkR, and want to import README.md
file, or just any file into sparkR.


Thanks in advance.


Best,
Wei


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