function?checkCostFunction（lambda）
%CHECKCOSTFUNCTION?Creates?a?collaborative?filering?problem?
%to?check?your?cost?function?and?gradients
%???CHECKCOSTFUNCTION（lambda）?Creates?a?collaborative?filering?problem?
%???to?check?your?cost?function?and?gradients?it?will?output?the?
%???analytical?gradients?produced?by?your?code?and?the?numerical?gradients?
%???（computed?using?computeNumericalGradient）.?These?two?gradient?
%???computations?should?result?in?very?similar?values.

%?Set?lambda
if?~exist（‘lambda‘?‘var‘）?||?isempty（lambda）
????lambda?=?0;
end

%%?Create?small?problem
X_t?=?rand（4?3）;
Theta_t?=?rand（5?3）;

%?Zap?out?most?entries
Y?=?X_t?*?Theta_t‘;
Y（rand（size（Y））?>?0.5）?=?0;
R?=?zeros（size（Y））;
R（Y?~=?0）?=?1;

%%?Run?Gradient?Checking
X?=?randn（size（X_t））;
Theta?=?randn（size（Theta_t））;
num_users?=?size（Y?2）;
num_movies?=?size（Y?1）;
num_features?=?size（Theta_t?2）;

numgrad?=?computeNumericalGradient（?...
????????????????@（t）?cofiCostFunc（t?Y?R?num_users?num_movies?...
????????????????????????????????num_features?lambda）?[X（:）;?Theta（:）]）;

[cost?grad]?=?cofiCostFunc（[X（:）;?Theta（:）]??Y?R?num_users?...
??????????????????????????num_movies?num_features?lambda）;

disp（[numgrad?grad]）;
fprintf（[‘The?above?two?columns?you?get?should?be?very?similar.\n‘?...
?????????‘（Left-Your?Numerical?Gradient?Right-Analytical?Gradient）\n\n‘]）;

diff?=?norm（numgrad-grad）/norm（numgrad+grad）;
fprintf（[‘If?your?backpropagation?implementation?is?correct?then?\n‘?...
?????????‘the?relative?difference?will?be?small?（less?than?1e-9）.?\n‘?...
?????????‘\nRelative?Difference:?%g\n‘]?diff）;

end

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----

?????文件???????1620??2013-11-18?21:58??cross-filter\checkCostFunction.m

?????文件???????2471??2013-12-18?19:28??cross-filter\cofiCostFunc.m

?????文件???????1095??2013-11-18?21:58??cross-filter\computeNumericalGradient.m

?????文件???????7093??2013-12-18?15:02??cross-filter\ex8_cofi.m

?????文件?????201196??2013-11-18?21:58??cross-filter\ex8_movieParams.mat

?????文件?????223396??2013-11-18?21:58??cross-filter\ex8_movies.mat

?????文件???????8742??2013-11-18?21:58??cross-filter\fmincg.m

?????文件????????651??2013-11-18?21:58??cross-filter\loadMovieList.m

?????文件??????48444??2013-11-18?21:58??cross-filter\movie_ids.txt

?????文件????????479??2013-11-18?21:58??cross-filter\normalizeRatings.m

?????文件????????582??2013-11-18?21:58??cross-filter\visualizeFit.m

?????目錄??????????0??2014-01-07?18:18??cross-filter

-----------?---------??----------?-----??----

???????????????495769????????????????????12