我有小波变换代码。他们在这里使用coif1来分解信号。任何人都可以解释一下coif1的用途吗？这是什么意思？
这是代码：
function wavelet = waveletTransform(image)
% input: image to process and extract wavelet coefficients from
% output: 1x20 feature vector containing the first 2 moments of wavelet
% coefficients
imgGray = double(rgb2gray(image))/255;
imgGray = imresize(imgGray, [256 256]);
coeff_1 = dwt2(imgGray', 'coif1');
coeff_2 = dwt2(coeff_1, 'coif1');
coeff_3 = dwt2(coeff_2, 'coif1');
coeff_4 = dwt2(coeff_3, 'coif1');
% construct the feaute vector
meanCoeff = mean(coeff_4);
stdCoeff = std(coeff_4);
wavelet = [meanCoeff stdCoeff];
end