# How to apply this formula into a matlab loop?

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Hi, I have a table that looks like this:

% have: % wanted:

X Y Z

____________________________

A 1 2

B 2 2

C 3 -2

D 4 -2

A 5 2

B 6 2

C 7 -2

D 8 -2

A 9 2

B 10 2

C 11 -2

D 12 -2

I need to create a vector Z that only uses values when X=B or X=D and is solved as follows:

Z(1) = Y(4)-Y(2)

Z(2) = Y(4)-Y(2)

Z(3) = Y(4)-Y(6)

Z(4) = Y(4)-Y(6)

Z(5) = Y(8)-Y(6)

Z(6) = Y(8)-Y(6)

Z(7) = Y(8)-Y(10)

Z(8) = Y(8)-Y(10)

Z(9) = Y(12)-Y(10)

Z(10) = Y(12)-Y(10)

etc...

(note that the actual data has different numbers so it's not actually as easy as just creating a vector of 2s and -2s)

I'm struggling to implement this into matlab, e.g. in a loop... I hope someone can help me out!

Thanks

##### 0 Comments

### Answers (1)

Esha Chakraborty
on 28 Jan 2022

I understand that Z(i) = Y(b) - Y(a), where variables a and b are incremented by 4 after every 4 iterations. For this, you can use "rem" function inside "for" loop and iterate over the rows of the table. Then, embed the “if” statement inside to choose the values for subtraction.

Use the below code for reference:

a = 0;

b = 2;

rows = 10;

for i = 1:rows %Can be modified as per requirements

if rem(i,4) == 3

b = b + 4;

end

if rem(i,4) == 1

a = a + 4;

end

Z(i) = Y(b) - Y(a);

disp(Z);

end

##### 2 Comments

Esha Chakraborty
on 1 Feb 2022

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