Additional file 2 of Modeling the effect of age on quantiles of the incubation period distribution of COVID-19

Additional file 2 1. Data file path To ensure that the program runs successfully, the data file “Additional file 1.xls” should be placed in the current working directory of R, which can be shown by running the code “getwd()” in R. An alternative way is adding the file path in Line 18 of the code. 2. R packages needed R packages including “readxl” “splines” “ggplot2” “quantreg” and “SparseM” should be successfully installed before running the program. All the packages can be installed by running “install.packages()”, such as “install.packages(“readxl”)” for package “readxl”.