Several representative LAMOST spectra with various configurations on parameters and their corresponding best-fitting templates. The black line indicates a test spectrum, the red line indicates its best-fitting template, and the yellow line indicates the residual between them. The best-fitting template is determined based on the Euclidean distance between the test spectrum and each training spectrum in stellar parameter space (the parameters of the test spectrum are estimated using the SPEMR model). This figure only shows three stellar atmospheric parameters for each spectrum due to space limitations.