How to count the number of points above and below a line

I need to write a function that takes x and y coordinates in a matrix and sums if they are above and on a straight line or below the line in different cells [above, below]. I have been provided the slope (m), and the intercept (b), and the (x,y) coordinates. I have really no idea where to start with this function so I was hoping someone better at matlab might have an idea how I should approach this function. Greatly appreciate it.

Answer 1

[Adam Danz]

Let's say x stores all of the x-values of your coordinates. Compute the y-value on the line for each x-value.

yLine = m.*x + b; 

If yLine is less than the original y coordinates, then the y coordinates are above or on the line.

isAboveOrOnLine = y >= yLine;