Need help with my face recognition

Hi,
I need help with my face recognition program.
I got these errors when i build my program:

error LNK2019: unresolved external symbol "public: virtual void __thiscall cv::HOGDescriptor::setSVMDetector(class std::vector<float,class std::allocator<float> > const &)" (?setSVMDetector@HOGDescriptor@cv@@UAEXABV?$vector@MV?$allocator@M@std@@@std@@@Z) referenced in function "int __cdecl ppledetect(void)" (?ppledetect@@YAHXZ)    

error LNK2001: unresolved external symbol "public: virtual void __thiscall cv::HOGDescriptor::write(class cv::FileStorage &,class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &)const " (?write@HOGDescriptor@cv@@UBEXAAVFileStorage@2@ABV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z)

error LNK1120: 11 unresolved externals

I got 11 these kinds of errors.
3 of error LNK2019 while 8 of error LNK2001 and 1 of error LNK1120.
Why is this happening?
Can someone pls help me?
Thanks.

Tags: C++, Linker, Errors, Compilation