24. The system of claim 17 , wherein obtaining a weighted semantic graph comprises: obtaining the analyzed corpus, the analyzed corpus comprising more than 5000 documents; for each document in the analyzed corpus, with one or more processers: determining a respective n-gram vector, each n-gram vector comprising a plurality of values each indicating presence of a respective n-gram in text of the respective document, wherein the n-gram vectors indicate at least 500 values and correspond to at least some n-grams including three words; determining the scores indicating the amount of semantic similarity relative to the other documents in the analyzed corpus based on angles between the n-gram vector of the respective document and n-gram vectors of the other documents in the analyzed corpus.
24. The system of claim 17 , wherein obtaining a weighted semantic graph comprises: obtaining the analyzed corpus, the analyzed corpus comprising more than 5000 documents; for each document in the analyzed corpus, with one or more processers: determining a respective n-gram vector, each n-gram vector comprising a plurality of values each indicating presence of a respective n-gram in text of the respective document, wherein the n-gram vectors indicate at least 500 values and correspond to at least some n-grams including three words; determining the scores indicating the amount of semantic similarity relative to the other documents in the analyzed corpus based on angles between the n-gram vector of the respective document and n-gram vectors of the other documents in the analyzed corpus. 25. The system of claim 24 , the operations comprising: determining the edges based on which of the scores indicating the amount of semantic similarity satisfy a threshold.