BP神經(jīng)網(wǎng)絡(luò)matlab教程

1、1會(huì)計(jì)學(xué)BP神經(jīng)網(wǎng)絡(luò)神經(jīng)網(wǎng)絡(luò)matlab教程教程1x2x1Nx1y2y2Ny1z2z3Nz123N1T2Tihwhjw- - -隱含層輸出層輸入層3NT1122.nnnetx wx wx w1f()1enetynet211f ()(1)1e(1e)-netnetnetyy根據(jù)根據(jù)S S型激活函數(shù)的圖形可知型激活函數(shù)的圖形可知, ,對(duì)神經(jīng)網(wǎng)絡(luò)進(jìn)行訓(xùn)練，應(yīng)該將對(duì)神經(jīng)網(wǎng)絡(luò)進(jìn)行訓(xùn)練，應(yīng)該將netnet的值盡的值盡量控制在收斂比較快的范圍內(nèi)量控制在收斂比較快的范圍內(nèi) 將誤差分?jǐn)偨o各層的所有將誤差分?jǐn)偨o各層的所有單元各層單元的誤單元各層單元的誤差信號(hào)差信號(hào)修正各單元權(quán)修正各單元權(quán)值值12,nxxxx12,

2、phihihihi12,pho hohoho12,qyiyiyiyi12,qyoyoyoyo12,qdddodihwf( ) howhb1,2,kmob211( )( )2qoooedkyo kk12( )( ),( ),( )nkx kx kx kx12( )( ),( ),( )qkd kdkdkod1( )( )1,2,nhihihihikw x kbhp( )f( )1,2,hhho khi khp1( )( )1,2,pohohohyi kw ho kboq( )f( )1,2,ooyo kyi koqohoohoeeyiwyiw( )( )( )phohoohhhohow ho k

3、byi kho kww211( ( )( )2( ( )( )( )( ( )( )f( )( )qooooooooooood kyo ked kyo k yo kyiyid kyo kyi kk( )ok( )( )oohhoohoeeyik ho kwyiw 1( )( )( )( )( )hihhihnihihhiiihiheehikwhikww x kbhikx kwwp第五步，利用隱含層到輸出層的連接權(quán)第五步，利用隱含層到輸出層的連接權(quán)值、輸出層的值、輸出層的 和隱含層的輸出計(jì)算誤和隱含層的輸出計(jì)算誤差函數(shù)對(duì)隱含層各神經(jīng)元的偏導(dǎo)數(shù)差函數(shù)對(duì)隱含層各神經(jīng)元的偏導(dǎo)數(shù) 。 ( )hk( )o

4、k21212111( )( ) )( )2( )( )( )1( )f( ) )( )2( )( )1( )f( ) )( )2( )( )qoohohhhqoohohhqpohohohohhhd kyo keho khi kho khi kd kyi kho kho khi kd kw ho kbho kho khi k11( )( )( )f ( )( )( )f ( )( )qhooohoohqohohhoho kd kyo kyi kwhi kk whi kk 1( )( )( )( )( )hoohhoNNhohoohewkk ho kwwwk ho k ( )ok( )howk(

5、)hk1( )( )( ) ( )( )( ) ( )hihhiihhihNNihihhieehi kw kk x kwhi kwwwk x k2111( )( )2qmookoEdky kmwhohoewe0，此時(shí)，此時(shí)who0hoewe0who函函 數(shù)數(shù) 名名功功 能能newff()生成一個(gè)前饋生成一個(gè)前饋BP網(wǎng)絡(luò)網(wǎng)絡(luò)tansig()雙曲正切雙曲正切S型型(Tan-Sigmoid)傳輸函數(shù)傳輸函數(shù)logsig()對(duì)數(shù)對(duì)數(shù)S型型(Log-Sigmoid)傳輸函數(shù)傳輸函數(shù)traingd()梯度下降梯度下降BP訓(xùn)練函數(shù)訓(xùn)練函數(shù)月份月份123456銷量銷量205623952600229816341600月份月份789101112銷量銷量1873147819001500204615561122.nnnetx wx wx w1f()1enetynet12,nxxxx12,phihihihi12,pho hohoho12,qyiyiyiyi12,qyoyoyoyo12,qdddod( )hk1( )( )( ) ( )( )( ) ( )hihhiihhihNNihihhieehi kw kk x kwhi kwwwk x khoewe0who函函 數(shù)數(shù) 名名功功 能能newff()生成一個(gè)前饋生成一個(gè)前饋BP網(wǎng)絡(luò)網(wǎng)絡(luò)tansig()雙曲