machine learning ex4

function checkNNGradients（lambda）
%CHECKNNGRADIENTS Creates a small neural network to check the
%backpropagation gradients
%   CHECKNNGRADIENTS（lambda） Creates a small neural network to check the
%   backpropagation gradients it will output the analytical gradients
%   produced by your backprop code and the numerical gradients （computed
%   using computeNumericalGradient）. These two gradient computations should
%   result in very similar values.
%

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

input_layer_size = 3;
hidden_layer_size = 5;
num_labels = 3;
m = 5;

% We generate some ‘random‘ test data
Theta1 = debugInitializeWeights（hidden_layer_size input_layer_size）;
Theta2 = debugInitializeWeights（num_labels hidden_layer_size）;
% Reusing debugInitializeWeights to generate X
X  = debugInitializeWeights（m input_layer_size - 1）;
y  = 1 + mod（1:m num_labels）‘;

% Unroll parameters
nn_params = [Theta1（:） ; Theta2（:）];

% Short hand for cost function
costFunc = @（p） nnCostFunction（p input_layer_size hidden_layer_size ...
                               num_labels X y lambda）;

[cost grad] = costFunc（nn_params）;
numgrad = computeNumericalGradient（costFunc nn_params）;

% Visually examine the two gradient computations.  The two columns
% you get should be very similar. 
disp（[numgrad grad]）;
fprintf（[‘The above two columns you get should be very similar.
‘ ...
         ‘（Left-Your Numerical Gradient Right-Analytical Gradient）

‘]）;

% Evaluate the norm of the difference between two solutions.  
% If you have a correct implementation and assuming you used EPSILON = 0.0001 
% in computeNumericalGradient.m then diff below should be less than 1e-9
diff = norm（numgrad-grad）/norm（numgrad+grad）;

fprintf（[‘If your backpropagation implementation is correct then 
‘ ...
         ‘the relative difference will be small （less than 1e-9）. 
‘ ...
         ‘
Relative Difference: %g
‘] diff）;

end

 属性            大小     日期    时间   名称
----------- ---------  ---------- -----  ----
     目录           0  2017-03-14 09:40  jiqixuexi-ex4
     目录           0  2017-03-14 09:40  jiqixuexi-ex4练习4
     文件        1950  2017-03-14 09:40  jiqixuexi-ex4练习4checkNNGradients.m
     文件        1095  2017-03-14 09:40  jiqixuexi-ex4练习4computeNumericalGradient.m
     文件         841  2017-03-14 09:40  jiqixuexi-ex4练习4debugInitializeWeights.m
     文件        1502  2017-03-14 09:40  jiqixuexi-ex4练习4displayData.m
     文件        8099  2017-03-14 09:40  jiqixuexi-ex4练习4ex4.m
     文件     7511764  2017-03-14 09:40  jiqixuexi-ex4练习4ex4data1.mat
     文件       79592  2017-03-14 09:40  jiqixuexi-ex4练习4ex4weights.mat
     文件        8749  2017-03-14 09:40  jiqixuexi-ex4练习4fmincg.m
     目录           0  2017-03-14 09:40  jiqixuexi-ex4练习4lib
     目录           0  2017-03-14 09:40  jiqixuexi-ex4练习4libjsonlab
     文件        1624  2017-03-14 09:40  jiqixuexi-ex4练习4libjsonlabAUTHORS.txt
     文件        3862  2017-03-14 09:40  jiqixuexi-ex4练习4libjsonlabChangeLog.txt
     文件         881  2017-03-14 09:40  jiqixuexi-ex4练习4libjsonlabjsonopt.m
     文件        1551  2017-03-14 09:40  jiqixuexi-ex4练习4libjsonlabLICENSE_BSD.txt
     文件       18732  2017-03-14 09:40  jiqixuexi-ex4练习4libjsonlabloadjson.m
     文件       15574  2017-03-14 09:40  jiqixuexi-ex4练习4libjsonlabloadubjson.m
     文件         771  2017-03-14 09:40  jiqixuexi-ex4练习4libjsonlabmergestruct.m
     文件       19369  2017-03-14 09:40  jiqixuexi-ex4练习4libjsonlabREADME.txt
     文件       17462  2017-03-14 09:40  jiqixuexi-ex4练习4libjsonlabsavejson.m
     文件       16123  2017-03-14 09:40  jiqixuexi-ex4练习4libjsonlabsaveubjson.m
     文件        1094  2017-03-14 09:40  jiqixuexi-ex4练习4libjsonlabvarargin2struct.m
     文件        1195  2017-03-14 09:40  jiqixuexi-ex4练习4libmakeValidFieldName.m
     文件        5562  2017-03-14 09:40  jiqixuexi-ex4练习4libsubmitWithConfiguration.m
     文件        3210  2017-03-14 09:40  jiqixuexi-ex4练习4
nCostFunction.m
     文件         585  2017-03-14 09:40  jiqixuexi-ex4练习4predict.m
     文件         903  2017-03-14 09:40  jiqixuexi-ex4练习4
andInitializeWeights.m
     文件         137  2017-03-14 09:40  jiqixuexi-ex4练习4sigmoid.m
     文件         677  2017-03-14 09:40  jiqixuexi-ex4练习4sigmoidGradient.m
     文件        1635  2017-03-14 09:40  jiqixuexi-ex4练习4submit.m
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