warning: No usable data in this plot to auto-scale axis range或是
All points x value undefined
warning: Skipping data file with no valid points最後在無意間, 使用awk "{print $1,$2 }"來測試資料檔時, 從它的輸出結果中, 發現可能的問題:
all points undefined!
原始數據檔案的編碼(encode)。因為數位記錄器預設的輸出格式為Unicode, 而在gnuplot以及awk無法正確輸入, 而造成不預期的結果。使用記事本(notepad)將原始數據檔, 以另存新檔時, 將編碼改為UTF-8, 以及在gnuplot中,要輸入 set encoding utf8 就可以將問題解決了。
In short:
Gnuplot recognizes data file encoded in UTF-8. If a unicode encoded data file is used in gnuplot, unexpected results will happen. In order to read UTF-8 data file correctly, "set encoding utf8" should be used in gnuplot.