# Finding out values for elements of an array from corresponding array elements?

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Tha saliem on 10 Jan 2018
Commented: Tha saliem on 10 Jan 2018
hi
i have calculated weights given below between elements of a matrix using some mathematics
weights= {[0.79,0.31,0.24,0.71,0.1],[0.79,0.12,0.71,0.62,0.24]}
Here
[0.79,0.31,0.24,0.71,0.1]
represents weight between 1 and 2,3,4,5,6 (0.79 for 1,2 ; 0.31 for 1,3 and so on) AND
[0.79,0.12,0.71,0.62,0.24]
represents weights between 2 and 1,3,4,5,6 (0.79 between 2,1 ; 0.12 between 2 and 3 and so on)
We can say that values of diagonal elements like 1,1 ; 2,2 are not there in weights.
Now I have another array X And I need weights of these elements from corresponding weights cell. LIKE for 3, weight of 1,3 will be taken as an output which is 0.31 in this case
X={[3;5;6;8];{[1;5;6;8]}}
Problem is that if i try to get this using loop: weight of 3 is at index position 2 in weights. For first row we can use loop using index-1. BUT when it comes to 2nd row this will not work weight for index 1 is at index 1 in weights{1,2}. But for 5 is at index 4 in weights{1,2}. confused about how to do this.
Also there are not just 2 rows. They are large in number.
Kindly help to solve this
THANK YOU

Thorsten on 10 Jan 2018
You can represent your weights as a matrix using NaN for the diagonal elements that do not exist:
Weights = [NaN, 0.79,0.31,0.24,0.71,0.1;
0.79, NaN, 0.12,0.71,0.62,0.24];
Then you can simply get the proper weight for row i, column j as
Weights(i, j)

#### 1 Comment

Tha saliem on 10 Jan 2018
Thank You for help.

dpb on 10 Jan 2018
I think simplest solution would be to just augment the weights array by a placeholder for the missing diagonal positions; then there's a straight 1:1 lookup. Use NaN as a marker if need a unique way to select the non-diagonal members only.

#### 1 Comment

Tha saliem on 10 Jan 2018
Yes Thank You.