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Table 2 N-gram feature templates of the ith character

From: Multi-task learning for Chinese clinical named entity recognition with external knowledge

Types Template
2-gram \(x_{i-1}x_i, x_ix_{i+1}\)
3-gram \(x_{i-2}x_{i-1}x_i, x_ix_{i+1}x_{i+2}\)
4-gram \(x_{i-3}x_{i-2}x_{i-1}x_i, x_ix_{i+1}x_{i+2}x_{i+3}\)
5-gram \(x_{i-4}x_{i-3}x_{i-2}x_{i-1}x_i, x_ix_{i+1}x_{i+2}x_{i+3}x_{i+4}\)
6-gram \(x_{i-5}x_{i-4}x_{i-3}x_{i-2}x_{i-1}x_i, x_ix_{i+1}x_{i+2}x_{i+3}x_{i+4}x_{i+5}\)