download-nhanes:用于下载和格式化 NHANES 数据的 R 函数

download-nhanes =============== R function to download and format NHANES data. The user can specify desired data by year and by section (demog, dietary, exam, lab, questionnaire). When complete, the function will download the data from the CDC FTP site, merge it, compute multiyear weights, and return a weighted survey object ready for analysis.