Flag positions in a vector number where values fall above or below a certain threshold
I'm not sure how to describe this question, so I'll just write some code to illustrate what I'm trying to achieve.
numberVector = c(56,23,10,26,11,9,33,60,71,1)
xaxisVector = c(1:length(numberVector))
booleanVector = c(FALSE,TRUE,FALSE,FALSE,FALSE,FALSE,FALSE,TRUE,FALSE,TRUE)
plot(xaxisVector,numberVector)
abline(a=50,b=0,col="red")
points(xaxisVector[booleanVector],numberVector[booleanVector],col="blue",pch=20)
As you can see, the above code creates a graph that looks like below.
As you can see, every time the value in numberVector goes from above 50 to below 50, I highlight the point in blue. (for example 56 to 23, 23 is highlighted) And every time the value in numberVector goes from below 50 to over 50, I highlight the point in blue. (e.g. 33 to 60, 60 stands out)
I manually typed boolean values into booleanVector. But how would I generate such a vector of booleans if there was any vector like numberVector?
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We can look at different signs of minus fifty. for example
booleanVector2 <- c(FALSE, diff(sign(numberVector-50))!=0)
all(booleanVector==booleanVector2)
# [1] TRUE
sign(x-50)
basically tracks if it is above or below the line. The diff()
difference between pairs of values for looking for changes is considered. We add FALSE because we assume the first value starts on one side of the string.
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