If statement and storage

General
1

Hello House,
Good day.
Please I have problem with the short code below and needs advice/direction accordingly. I have an input data (X) ranging from 2 to 40 at 2.5 interval. The length of X and Z datasets are 16. I am writing a conditional statement such that: for i = 1, Z[i] > 0, X =X[i] and for Z[i] = 0, X = 0.. Please note that i =1:16. The values of X and Z are found below:


X =  seq(2, 40, 2.5)
Z = c(2, 1, 0, 4, 1, 1, 3, 0, 8, 1, 21, 0, 10, 0, 1, 5)

X <- matrix(X, nrow = length(X), byrow = TRUE) 

Z <- matrix(Z, nrow = length(Z), byrow = TRUE) 

head(X)
head(Z)

length(X)
length(Z)

d = NULL
df = NULL

for (i in 1:length(X)){

p = X[i]
r = Z[i]

p
r

temporary_function <- function(r) {

if (r > 0){
         (p) 
} 
else { 
         (0) 
}
}
}
mapply(FUN = temporary_function, X)
2

Hi @Zakky,
If I understand your question, you want to update X[i] to 0 every time the corresponding Z[i] == 0, otherwise leave X[i] as is. Is this correct? Secondly, is using loops and mapply a requirement?

The easiest and fastest approach is to take advantages of R's vectorization.

You can test the equality of Z == 0, which returns a logical vector/matrix
where the condition is either true or false.

 Z == 0

      [,1]
 [1,] FALSE
 [2,] FALSE
 [3,]  TRUE
 [4,] FALSE
 [5,] FALSE
 [6,] FALSE
 [7,] FALSE
 [8,]  TRUE
 [9,] FALSE
[10,] FALSE
[11,] FALSE
[12,]  TRUE
[13,] FALSE
[14,]  TRUE
[15,] FALSE
[16,] FALSE`

From here, you can use this test of equality as a way to index the positions of X and update
it where the Z == 0 is TRUE.

X[Z == 0] <- 0

giving

X
     [,1]
[1,]  2.0
[2,]  4.5
[3,]  0.0
[4,]  9.5
[5,] 12.0
[6,] 14.5
[7,] 17.0
[8,]  0.0
[9,] 22.0
[10,] 24.5
[11,] 27.0 
[12,]  0.0
[13,] 32.0
[14,]  0.0
[15,] 37.0  
[16,] 39.5
3

Hello, sorry for my late response.

you want to update X[i] to 0 every time the corresponding Z[i] == 0, otherwise leave X[i] as is. Is this correct? YES PLS

Secondly, is using loops and mapply a requirement? NOT REALLY.

I got ur suggestion and it works out for me. Thank you so much.

4

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5

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