For example ..
I have a series of values (prices) related to a product on several different dates.
I need to get the percentage change of this value.
Currently, prices are giving a standard deviation of 120.00, but I wanted that result in percentage. Like, prices have varied by 20% on those specific days.
How to do this in R?
If you want to know the standard deviation relative to the mean, this is the coefficient of variation . To have in percentage just multiply by one hundred.
Programming the CV in R is a very easy problem to solve.
coefVar <- function(x, na.rm = FALSE){
sd(x, na.rm = na.rm)/mean(x, na.rm = na.rm)
}
set.seed(9580) # Torna os resultados reprodutíveis
x <- runif(100, 0, 20)
coefVar(x)
#[1] 0.621354
coefVar(x)*100 # Em porcentagem
#[1] 62.1354
Given the comment about the result of a function calculation, this is what gives me:
y <- c(772.8, 147.28, 993.72)
coefVar(y)*100
#[1] 68.82238
It seems right.