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Figure 1
Google Trends graph showing (a) weekly search popularity of “obesity,” (b) monthly search popularity of “14,” and (c) average search trend of all the queries related to topic “child obesity.”
Figure 2
The overall framework of the methodology, where (1) p(z|d) denotes the probability that document d belongs to topic z; (2) β denotes the keywords’ effects on topics, that is, the coefficients of X; (3) spike γ can make most of the coefficients of X zeros, which ensures that the stepwise regression process will run correctly; and (4) Y – Z*α (regression component) refers to publication data with the time-series component, where tendency and seasonal components are not included.
Figure 3
The monthly number of publications on (a) “child obesity” and (b) “diabetes” over time.
Figure 4
Trends of topics (a) “child obesity” and (b) “diabetes.” The x-axis represents time from January 2004 to January 2013; the y-axis represents the number of publications within a month on “child obesity” and “diabetes,” respectively. Growth rate of topics (c) “child obesity” and (d) “diabetes.” The x-axis represents time from January 2004 to January 2013; the y-axis represents the growth rate of publications within a month on “child obesity” and “diabetes,” respectively.
Figure 5
Seasonal effect for topics (a) “child obesity” and (b) “diabetes” from January 2008 to January 2013.
Figure 6
Regression components for obesity topics (a) “child obesity” and (b) “diabetes” over time.