CODEWITHSUNDEEP
rloopsif-statementmatrix
student_s
student_s

Reputation: 11

for loop with if statement to compare matrices and fill new matrix

I have two matrices, matrix A and matrix B (5 x 5). I randomly assigned values between 0 and 4 to matrix A.

Now, for example, I want to check if A[1,2] > A[2,1]. If that holds true I want to assign a specific value to B[1,2] and B[2,1]. In this case it should be B[1,2] = 3 and B[2,1] = 0. If A[1,2] < A[2,1] it should be the other way around; e.g. B[1,2] = 0 and B[2,1] = 3. If A[1,2] == A[2,1] it should be B[1,2] = 1 and B[2,1] = 1.

I am looking for an R code to do this as a loop to fill matrix B completely with the right values of either 0,1 or 3.

I would really appreciate any help! Thank you very much in advance!

Matrix A

If the outcome of R is matrix A, matrix B should look like the self-drawn matrix.

Matrix B

Upvotes: 1

Views: 141

Answers (1)

ThomasIsCoding
ThomasIsCoding

Reputation: 101209

We can do like this

> `diag<-`(3 * (A > t(A)) + 1 * (A == t(A)), NA)
     [,1] [,2] [,3]
[1,]   NA    3    0
[2,]    0   NA    1
[3,]    3    1   NA

Upvotes: 1

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