光学学报, 2019, 39 (9): 0930002, 网络出版: 2019-09-09   

特征变量选择和回归方法相结合的土壤有机质含量估算 下载: 1176次

Estimation of Soil Organic Matter Content Based on Characteristic Variable Selection and Regression Methods
作者单位
1 青海师范大学地理科学学院,青海省自然地理与环境过程重点实验室, 青海 西宁 810008
2 中国环境科学研究院, 北京 100012
图 & 表

图 1. 研究区位置及采样点分布图

Fig. 1. Location of the study area and distribution of soil sampling sites

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图 2. 土壤样品反射率曲线。(a) 原始光谱;(b) MSC-MF-1st Derivative预处理光谱

Fig. 2. Spectral reflectance curves of soil samples. (a) Raw spectra; (b) spectra after MSC-MF-1st Derivative pre-processing

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图 3. sCARS变量筛选流程。(a)变量变化趋势;(b)十折交叉均方根误差;(c)变量回归系数

Fig. 3. Variable selection process by sCARS. (a) Changing trend of variables; (b) 10-fold RMSECV values; (c) regression coefficients of variables

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图 4. GA特征变量筛选过程

Fig. 4. Characteristic variable selection process by GA

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图 5. 预处理光谱sCARS-SPA特征变量筛选过程。(a)模型变量数;(b)变量指数

Fig. 5. Characteristic variable selection process by sCARS-SPA from the pre-processing spectrum. (a) Number of variables in the model; (b) variable index

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图 6. 不同变量筛选方法挑选特征变量分布

Fig. 6. Distribution of characteristic variables with different variable selection methods

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图 7. sCARS-PLSR模型预测SOM含量散点图

Fig. 7. Scatter plot for the measured and predicted value by sCARS-PLSR model

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图 8. SPA-SVM模型预测SOM含量散点图

Fig. 8. Scatter plot for the measured and predicted value by SPA-SVM model

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图 9. IRIV-RF模型预测SOM含量散点图

Fig. 9. Scatter plot for the measured and predicted value by IRIV-RF model

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图 10. 不同变量筛选方法PLSR、SVM、RF模型建模结果

Fig. 10. Results of PLSR, SVM and RF models with different variable selection methods

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图 11. 人工剔除异常值前后sCARS-RF模型散点图。(a)剔除异常值前;(b)剔除异常值后

Fig. 11. Scatter plots for the measured and predicted value by sCARS-RF model before and after artificially eliminating outliers. (a) Contain outliers; (b) eliminate outliers

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表 1校准集和验证集土壤有机质含量统计表

Table1. Soil organic matter content statistics of calibration set and validation set

Sample setSamplenumberMin /(g·kg-1)Max /(g·kg-1)Mean /(g·kg-1)SD
Calibration set2684.86148.7432.4723.52
Validation set1338.26133.5632.1622.44

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表 2不同变量筛选方法的PLSR模型精度

Table2. Accuracies of PLSR model with different variable selection methods

Selection methodVariable numberPCCalibration setValidation set
Rcal2RMSECALR2valRMSEVALRPD
Full-spectrum200050.8429.3260.8359.0692.5
sCARS5150.8748.3270.8837.7972.9
SPA550.8509.1030.8588.5252.6
GA18640.8429.3420.8618.4152.7
IRIV6360.8439.3000.8758.0432.8
sCARS-SPA1740.76511.3910.8488.7912.6

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表 3不同变量筛选方法的SVM建模精度

Table3. Accuracies of SVM model with different variable selection methods

Selection methodVariable numberOptimal parameterCalibration setValidation set
g (nuclear function)c (punishment coefficient)Rcal2RMSECALRval2RMSEVALRPD
Full-spectrum20000.0363.0310.917.2210.7411.5461.9
sCARS510.0213.0310.8818.1160.8777.9182.8
SPA50.0041.7410.8588.8550.8897.4773.0
GA1860.0121.7410.8678.5770.8718.0932.8
IRIV630.0213.0310.8698.4930.8648.3072.7
sCARS-SPA170.0112.8580.8778.2460.8738.0522.8

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表 4不同变量筛选方法RF建模精度

Table4. Accuracies of RF model with different variable selection methods

Selection methodVariable numberCalibration setValidation set
Rcal2RMSECALRval2RMSEVALRPD
Full-spectrum20000.9425.8170.9574.8404.6
sCARS510.9425.7810.9584.7804.7
SPA50.9306.5850.9545.0824.4
GA1860.9395.8940.9594.6994.8
IRIV630.9415.9270.9604.6564.8
sCARS-SPA170.9405.9100.9554.9714.5

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表 5人工剔除异常值后模型精度

Table5. Model accuracy after manually eliminating outliers

ModelCalibration setValidation set
Rcal2RMSECALRval2RMSEVALRPD
sCARS-PLSR0.9435.5380.9265.9873.7
sCARS-SVM0.9266.0920.9574.9034.6
sCARS-RF0.9853.2040.9882.8657.8

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李冠稳, 高小红, 肖能文, 肖云飞. 特征变量选择和回归方法相结合的土壤有机质含量估算[J]. 光学学报, 2019, 39(9): 0930002. Guanwen Li, Xiaohong Gao, Nengwen Xiao, Yunfei Xiao. Estimation of Soil Organic Matter Content Based on Characteristic Variable Selection and Regression Methods[J]. Acta Optica Sinica, 2019, 39(9): 0930002.

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