check normal distribution (shapilo.test)

Outlook often gives viewers a false impression. Shapiro.test function will test whether data are according to a normal distribution. When p-Value is more than 0.05, the distribution can be called "normal".

Samples below shows when data are extracted just from Monday to Friday without considering national holiday, it's not a normal distribution. However, other groups 1) workday (business day only), 2) all-day and 3) weekend (Saturday and Sunday) distribution are normal. The degree of each distribution is different, though.


> shapiro.test(i[weekday])

Shapiro-Wilk normality test
data:  i[weekday]
W = 0.97156, p-value = 0.02788

> shapiro.test(i[workday])

Shapiro-Wilk normality test
data:  i[workday]
W = 0.98811, p-value = 0.5692

> shapiro.test(i)

Shapiro-Wilk normality test

data:  i

W = 0.98489, p-value = 0.1182

> shapiro.test(i[weekend])

Shapiro-Wilk normality test

data:  i[weekend]

W = 0.95236, p-value = 0.07851