JavaRDD<MatrixEntry> entries = ata.toCoordinateMatrix().entries().toJavaRDD(); JavaRDD<String> output = entries.map(new Function<MatrixEntry, String>() { public String call(MatrixEntry e) { return String.format("%d,%d,%s", e.i(), e.j(), e.value()); } }); output.saveAsTextFile("data/output1");