[1] [1] Li Maosong, Li Sen, Li Yuhui. Studies on drought in the past 50 years in China［J］. Chinese Journal of Agrometeorology, 2003, 24(1): 7-10.

[2] [2] Ni Shenhai, Gu Ying, Yan Nana, et al. Research on agricultural drought assessment method based on information assimilation of moisture cycle simulation model and remote sensing image information［J］. China Rural Water and Hydropower, 2016(1): 51-54.

[3] [3] Lu H, Cao Z, Xiao Y, et al. Fine-grained maize tassel trait characterization with multi-view representations［J］. Computers and Electronics in Agriculture, 2015, 118: 143-158.

[4] [4] Camargo A, Smith J S. Image pattern classification for the identification of disease causing agents in plants［J］. Computers and Electronics in Agriculture, 2009, 66(2): 121-125.

[5] [5] Selim S Z, Ismail M A. K-means-type algorithms: A generalized convergence theorem and characterization of local optimality［J］. IEEE Transactions on Pattern Analysis and Machine Intelligence, 1984, 6(1): 81-87.

[6] [6] Lu Zhiying, Liu Hai, Jia Huizhen, et al. Recognition of hail and rainstorm based on the radar reflectivity image features［J］. Acta Physica Sinica, 2014, 63(18): 189201.

[7] [7] Pan Haibin, Zhang Wei, Cong Mingyu, et al. Image preprocessing algorithm for space target space-based detection［J］. Acta Optica Sinica, 2009, 29(9): 2402-2407.

[8] [8] Wu J Y. A image retrieval method based on color histogram［C］. Informatics in Control, Automation and Robotics, 2012, 133: 741-746.

[9] [9] Haralick R M, Shanmugam K, Dinstein I. Texture features for image classification［J］. IEEE Transactions on Systems, Man, and Cybernetics, 1973, 3(6): 610-621.

[10] [10] Liu Tao, Sun Chengming, Wang Lijian, et al. In-field wheatear counting based on image processing technology［J］. Transactions of the Chinese Society for Agricultural Machinery, 2014, 45(2): 282-290.

[11] [11] Zhang S W, Wang Z. Cucumber disease recognition based on global-local singular value decomposition［J］. Neurocomputing, 2016, 205: 341-348.

[12] [12] Chang Liping, Shen Weixing, Lin Zunqi. Algorithm for digital wavefront fitting based on singular value decomposition［J］. Acta Optica Sinica, 2006, 26(11): 1676-1680.

[13] [13] Zhang Xianda. Matrix analysis and applications［M］. Beijing: Tsinghua University Press, 2013.

[14] [14] Holland J H. Adaptation in natural and artificial systems: An introductory analysis with applications to biology, control, artificial intelligence［M］. Cambridge: MIT Press, 1992.

[15] [15] Chen Xiaofeng, Long Changjiang, Niu Zhiyou, et al. Classification research of Chinese medicine based on latent semantic analysis and NIR［J］. Acta Optica Sinica, 2014, 34(9): 0930001.

[16] [16] Fawcett T. An introduction to ROC analysis［J］. Pattern Recognition Letters, 2006, 27(8): 861-874.

[17] [17] Zhou Zhihua. Machine learning［M］. Beijing: Tsinghua University Press, 2016: 28-37.