CODEWITHSUNDEEP
rfunction
Joeri
Joeri

Reputation: 167

Multiple rows in a function calculation in R

I have the following data:

measurement <- c(1:30)
angle <- rnorm(30, 0, 0.4)
data.1 <- data.frame(measurement, angle)

And I want to make a function that returns a TRUE value for four different scenarios:

   1. When 'angle' >  0.3 
or 2. When 'angle' < -0.3 
or 3. When 'angle' + the previous 'angle' >  0.3 
or 4. When 'angle' + the previous 'angle' < -0.3

I tried it with a for loop, and I've tried it the following way, but I just don't know how to include the sum of the angle and the angle that is measured one time-step earlier (so what i'm doing here is wrong but how can i improve it? preferably on the computationally least strenuous way because I work with massive data-sets):

n<-data.1$angle
function1 <- function(n){
    return(n>0.3 | n<(-0.3) | (n+(n-1))>(0.3) | (n+(n-1))<(-0.3))
}

Sorry for being an R novice but after strolling through the labyrinth of R documentation I saw no other way but to ask it here. Thanks for helping!

Upvotes: 1

Views: 145

Answers (1)

Arun
Arun

Reputation: 118809

You can do it in a vectorised format instead of doing it for each angle one by one. 

abs(data.1$angle) > 0.3 | abs(data.1$angle + c(0, head(data.1$angle,-1))) > 0.3

abs(data.1$angle) > 0.3 - the first and second conditions.
abs(data.1$angle + c(0, head(data.1$angle,-1))) > 0.3 - takes all angles and adds the previous angle to it using c(0, head(., -1)). Then again check with abs for 0.3 and -0.3

I get:

# [1] FALSE  TRUE  TRUE  TRUE  TRUE FALSE  TRUE  TRUE FALSE  TRUE  TRUE  TRUE  TRUE  TRUE
# [15]  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE FALSE FALSE FALSE  TRUE  TRUE
# [29]  TRUE  TRUE

Upvotes: 6

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