Description Usage Arguments Details Value Note Author(s) References See Also Examples
Calculates proportion/percent differences between subsequent (or lagged) elements of a numeric vector.
1 
x 
Numeric vector. 
lag 
Controls spacing between proportion/percent differences. For example, lag of 1 means you want to calculate differences between elements 1 and 2, 2 and 3, 3 and 4, and so on; a lag of 2 means you want calculate differences between elements 1 and 3, 2 and 4, 3 and 5, and so on. 
percent 

Each proportion/percent difference is based on two numbers, say x1
and x2
. The proportion difference is defined as (x1  x2) / mean(x1, x2)
, and the percent difference is the same quantity multiplied by 100
. Notice that this is NOT proportion/percent change, which divides by the initial value x1
rather than the average of x1
and x2
. See pchanges
for the proportion/percent change operation.
Numeric vector.
This function uses C++ code to achieve a 34 times speed increase compared to the base R code: len < length(x); p1 < x[2: len]; p2 < x[1: (len  1)]; (p1  p2) / (0.5 * (p1 + p2))
.
Dane R. Van Domelen
Acknowledgment: This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE0940903.
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