I am trying to use QwtWeedingCurveFitter to plot large data efficiently. I use qwt-5.2.1, which doesn't have the class. So, I have got qwt_curve_fitter.[cpp/h] from https://qwt.svn.sourceforge.net/svnr...s/qwt-5.x/src/
and replaced with the existing files with the same name in qwt-5.2.1. I try to call the weeding class:
Qt Code: 
  1. QwtWeedingCurveFitter *fitter = new QwtWeedingCurveFitter();
To copy to clipboard, switch view to plain text mode 
Then, I get an error message attached below. It looks like a linking error, but I don't know why this is happening. When I try to use another class from the same file:
Qt Code:
To copy to clipboard, switch view to plain text mode 
Then, the program works. I am wondering why I can't use QwtWeedingCurveFitter class. Any suggestion would be greatly appreciated.

Qt Code: 
  1. compiling .\simple_test.cpp
  2. simple_test.cpp
  3. linking release\simple.exe
  4. simple_test.obj : error LNK2019: unresolved external symbol "__declspec(dllimpor
  5. t) public: __thiscall QwtWeedingCurveFitter::QwtWeedingCurveFitter(double)" (__i
  6. mp_??0QwtWeedingCurveFitter@@QAE@N@Z) referenced in function _main
  7. simple_test.obj : error LNK2001: unresolved external symbol "public: virtual cla
  8. ss QPolygonF __thiscall QwtWeedingCurveFitter::fitCurve(class QPolygonF const &)
  9. const " (?fitCurve@QwtWeedingCurveFitter@@UBE?AVQPolygonF@@ABV2@@Z)
  10. simple_test.obj : error LNK2019: unresolved external symbol "__declspec(dllimpor
  11. t) public: virtual __thiscall QwtWeedingCurveFitter::~QwtWeedingCurveFitter(void
  12. )" (__imp_??1QwtWeedingCurveFitter@@UAE@XZ) referenced in function "public: virt
  13. ual void * __thiscall QwtWeedingCurveFitter::`scalar deleting destructor'(unsign
  14. ed int)" (??_GQwtWeedingCurveFitter@@UAEPAXI@Z)
  15. release\simple.exe : fatal error LNK1120: 3 unresolved externals
To copy to clipboard, switch view to plain text mode