Need help creating a code

Hi,

I have a 8x2 matrix.

A= [-1 -1; 2 -2; 0 -1; -2 -2; -3 1;0 2; -3 4; -2 0]

I want to do two things:

1. I want to see how many values there are in total in the first column which are either equal to -2 or less than -2.

2. Of those values in column 1 that are either equal to -2 or less than -2, I want to know if the corresponding value in the 2nd column is either greater than or equal to 2 OR less than or equal to -2.

For the above example in the end I would want...

B= 4 (because there are 4 values in column 1 that are less than or equal to -2).
C= 2 (because of the 4 values in column 1 that are equal to or less than -2, only 2 of their corresponding numbers in column 2 are either greater than/equal to 2 OR less than/equal to -2.

[dpb]

This seems straightforward enough to request like in homework, "show your work" -- what have you done so far and where did you get stuck, precisely?

Answer 1

[Star Strider]

Not sure how you want them presented:

A= [-1 -1; 2 -2; 0 -1; -2 -2; -3 1;0 2; -3 4; -2 0];
A1le2 = A(:,1) <= -2;               % A(:,1) <= -2
B = sum(A1le2);                     % Number Of A(:,1) <= 2
A2ge2 = A(A1le2,2) >=  2;           % A(:,1) <= -2 & A(:,2) >= +2
A2le2 = A(A1le2,2) <= -2;           % A(:,1) <= -2 & A(:,2) <= -2
C = sum([A2ge2; A2le2]);            % Number Of A(:,1) <= 2 & A(:,2) >= +2 & A(:,2) <= -2

EDIT — Specified ‘B’, added ‘C’.

Answer 2

[Andrei Bobrov]

At = A(:,1) <= -2;
B = sum(At);
C = sum(At & abs(A(:,2))>=2);