The data contain time-series data of daily outpatient for 18 diseases, and 12 environmental factors. These environmental factors are particular matters with diameters less than 10 $\mu$meters ($PM_{10}$), particular matters with diameters less than 2.5 $\mu$meters ($PM_{2.5}$), ozone ($O_3$), carbon monoxide (CO), nitrogen oxide (NO), nitrogen dioxide ($NO_2$), sulfur dioxide ($SO_2$), temperature (T), precipitation (P), wind direction (WD), wind speed (WS), and relative humidity (RH).The daily outpatient visits were computed according to the 3 aged groups of outpatients (0-15, 16-65, and higher than 66 years old as discussed in Wang and Chau~\cite{bib21} and Chau and Wang~\cite{bib22}. A spectrum of 18 diseases was sorted based on the International Classification of Diseases, 9th Revision (ICD-9). These 18 diseases include the diseases of respiratory system, such as allergic rhinitis (AR), asthma, pneumonia, and chronic obstructive pulmonary disease (COPD); accidents; mental disorders (anxiety, dissociative, somatoform disorders); the digestive system, such as peptic ulcer disease (PUD), and chronic liver diseases and cirrhosis; circulatory system, such as cerebrovascular disease, heart disease, and hypertensive disease; diabetes mellitus; malignant neoplasm (cancer); genitourinary system (nephritis, nephritis, and nephrosis); musculoskeletal system, such as other disorders of soft tissues, osteoarthrosis and allied disorders, and spondylosis and allied disorders; and influenza.