为什么小波分解后的值比原来的大

为什么小波分解后的值比原来的大
x=(1:168)
y=[354.5 ,298.1 ,268.3 ,243.3 ,238.6 ,258.8 ,372.3 ,431.0 ,518.4 ,578.9 ,620.8 ,741.9 ,651.0 ,532.1 ,538.8 ,552.5 ,612.0 ,696.4 ,701.9 ,713.7 ,744.5 ,722.7 ,612.8 ,487.1 ,351.4 ,312.9 ,280.1 ,279.5 ,255.0 ,293.7 ,359.0 ,448.4 ,523.6 ,577.7 ,620.7 ,644.5 ,548.9 ,529.4 ,514.4 ,554.2 ,634.0 ,685.0 ,688.6 ,712.7 ,742.5 ,716.0 ,595.5 ,456.9 ,358.7 ,318.2 ,264.5 ,266.2 ,256.0 ,261.3 ,376.4 ,435.3 ,524.9 ,564.4 ,616.2 ,651.6 ,539.6 ,517.4 ,529.9 ,515.2 ,578.1 ,672.5 ,661.8 ,659.9 ,714.3 ,709.2 ,596.8 ,457.5,355.2 ,305.3 ,267.2 ,260.5 ,248.1 ,260.4 ,358.1 ,410.1 ,508.4 ,564.5 ,608.5 ,641.3 ,540.2 ,523.1 ,521.5 ,528.7 ,585.4 ,679.1 ,676.0 ,666.9 ,726.5 ,706.3 ,603.1 ,459.0 ,357.3 ,318.1 ,289.3 ,264.4 ,249.0 ,269.7 ,365.3 ,401.0 ,493.0 ,535.0 ,586.7 ,617.0 ,507.4 ,500.9 ,522.1 ,525.7 ,598.8 ,674.1 ,676.9 ,684.7 ,719.5 ,701.9 ,618.5 ,475.2 ,383.0 ,310.7 ,297.2 ,267.6 ,269.5 ,273.2 ,302.2 ,403.5 ,497.3 ,548.6 ,608.3 ,647.7 ,562.6 ,526.3 ,511.0 ,537.3 ,578.6 ,707.8 ,662.9 ,679.3 ,718.6 ,683.9 ,596.7 ,466.1 ,374.2 ,317.8 ,279.0 ,255.6 ,245.4 ,264.1 ,315.7 ,376.8 ,481.0 ,545.4 ,586.0 ,640.3 ,545.7 ,523.0,495.4 ,536.7 ,586.0 ,676.3 ,646.4 ,661.8,712.7 ,686.0 ,581.8 ,445.7];
p=polyfit(x,y,3);
[c,l]=wavedec(y,3,'db1');
[cd1,cd2,cd3]=detcoef(c,l,[1,2,3]);
ca3=appcoef(c,l,'db1',3);
subplot(5,1,1); plot(y);title('y');
subplot(5,1,2); plot(1:l(1),ca3);title('ca3');
subplot(5,1,3); plot(1:l(2),cd3);title('cd3');
subplot(5,1,4); plot(1:l(3),cd2);title('cd2');
subplot(5,1,5); plot(1:l(4),cd1);title('cd1');

小波分析(wavelet analysis),或小波变换、小波转换(wavelet transform)是指用有限长或快速衰减的、 为母小波(mother wavelet)的震荡波形来表示信号.该波彠被 缩放 和 平移 以匹配输入的信号.