Creating a Vector from a Loop in R

Question

enter image description here

Hello, I am entirely new to using R and experiencing some problems trying to develop the attached equation. Provided below is the general idea of what I am trying to code where PMU1 = omega and PMU2 = omega' from the images.

I am running into two problems that I see which is that Vh[i] is out of bounds for "i+1" when i = 7, and that I can't get a vector solution. The answer for evaluating the above omega matrix is Vh[i] = (0.25,0.25,0,0,0.5,0). I'll eventually be using a different matrix set, but I am just trying to generate a code from the equation.

PMU1 <- as.matrix(PMU1)
PMU2 <- as.matrix(PMU2)

m <- nrow(PMU1)
n <- ncol(PMU1)

for (j in 1:n)
  {
 Vh[i] <- sum(abs(PMU1[i,j]-PMU1[i+1,j]))
  }

Vh[i]

Please improve your question by more specifically describing what you are trying to achieve. Also share the code you have tried so far. — Till
– Till, Commented Mar 5, 2022 at 19:18
Your edit helps, but it still isn't a minimal reproducible example. See How to make a great R reproducible example? for some helpful tips in making a reproducible example. — John Coleman
– John Coleman, Commented Mar 5, 2022 at 19:51

John Coleman · Accepted Answer · 2022-03-05 20:24:52Z

3

While a more vectorized approach probably exists, a simple approach is to use sapply:

PMU <- matrix(c(0,1,1,1,1,1,1,0,0,1,1,1,1,1,0,0,0,0,0,1,1,0,0,0,0,0,1,1),nrow = 7)
V <- sapply(1:(nrow(PMU)-1),function(i)mean(PMU[i+1,]-PMU[i,]))

After running this code, V = 0.25 0.25 0.00 0.00 0.50 0.00

answered Mar 5, 2022 at 20:24

John Coleman

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3 Comments

akrun Over a year ago

You can also use rowMeans(diff(PMU))

IRTFM Over a year ago

@akrun. Need abs() and /n and some way to iterate across adjacent rows

akrun Over a year ago

@IRTFM Yes, you ar eright although it works with the example in the solution post

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