<div style="line-height:1.7;color:#000000;font-size:14px;font-family:arial">when compute perplexity with ngram, the usage is  ngram -lm language.lm -order 4 -ppl test.txt. <div>but now I want  <span style="line-height: 1.7;">compute perplexity with ngram from stdin, what's  the command should i use?</span></div></div><br><br><span title="neteasefooter"><span id="netease_mail_footer"></span></span>