Study of excitation-emission-matrix( EEMs) compression based on wavelet packet transform

Excitation- emission- matrix( EEMs) data have been compressed with a frequency grade threshold based on a Daubechies( db) wavelet packet transform. First,the tree of the wavelet packet was formulated; secondly,the best-tree was determined by the principle of minima; finally,the frequency grade threshold was used to compress the wavelet packet coefficient. Experimental data were used to test the compression ability of this method.The compression results indicated that wavelet packet compression could retain more information than wavelet compression. The frequency grade threshold method based on wavelet packets was adopted to compress EEMs. The frequency grade threshold method afforded higher reconstruction percentages and compression percentages than other threshold compression methods: the maximum reconstruction percentage reached 90%,and the compression percentage was larger than 98%,with errors between spectra of lower than 1%. With the use of parallel factor analysis( PARAFAC) of the original EEMs data and the compressed data,it was possible to obtain the characteristics of the excitation and emission spectra of each component. The results of PARAFAC show that wavelet packet transform can compress and recover the information in EEMs data effectively.