## Tf-idf Transformer > Tf-idf是術語頻率 - 逆文檔頻率的縮寫，是一種數字統計，旨在反映單詞對集合或語料庫中的文檔的重要程度。 ### 構造函數參數 `$samples`（array） - 適合tf-idf模型的樣本 ``` use Phpml\FeatureExtraction\TfIdfTransformer; $samples = [ [1, 2, 4], [0, 2, 1] ]; $transformer = new TfIdfTransformer($samples); ``` ***** ### 轉換 要轉換文本樣本集合，請使用`transform`方法。例： ``` use Phpml\FeatureExtraction\TfIdfTransformer; $samples = [ [0 => 1, 1 => 1, 2 => 2, 3 => 1, 4 => 0, 5 => 0], [0 => 1, 1 => 1, 2 => 0, 3 => 0, 4 => 2, 5 => 3], ]; $transformer = new TfIdfTransformer($samples); $transformer->transform($samples); /* $samples = [ [0 => 0, 1 => 0, 2 => 0.602, 3 => 0.301, 4 => 0, 5 => 0], [0 => 0, 1 => 0, 2 => 0, 3 => 0, 4 => 0.602, 5 => 0.903], ]; */ ```