I am new for learning Spark MLlib. When I was reading about the example of Binomial logistic regression, I don't understand the format type of "libsvm". (Binomial logistic regression)
The text looks like:
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Can you help me to understand the format type of libsvm of Spark MLlib? Thanks!
The LibSVM format is quite simple. The first row contains the class label, in this case 0 or 1. Following that are the features, here there are two values for each one; the first one is the feature index (i.e. which feature it is) and the second one is the actual value.
The feature indices starts from 1 (there is no index 0) and are in ascending order. The indices not present on a row are 0.
In summary, each row looks like this;
<label> <index1>:<value1> <index2>:<value2> ... <indexN>:<valueN>
This format is advantageous to use when the data is sparse and contain lots of zeroes. All 0 values are not saved which will make the files both smaller and easier to read.
来源：https://stackoverflow.com/questions/44965186/how-to-understand-the-format-type-of-libsvm-of-spark-mllib