libSVM format

- sparse 한 데이터 저장

##for observation 1 to n, feature 1 to i
{target column_1} {feature index 1} : {feature value 1} ... {feature index k} : {feature value k}
...
{target column_n} {feature index 2} : {feature value 2} ... {feature index i} : {feature value i}

https://stackoverflow.com/questions/44965186/how-to-understand-the-format-type-of-libsvm-of-spark-mllib

How to understand the format type of libsvm of Spark MLlib?

공식 docum :  https://spark.apache.org/docs/2.0.2/mllib-data-types.html