Need help vertically/horizontally scanning a binary matrix with reference to an indexed point!

Aydin Akyol

2018 5 30

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So I have a binary matrix (just zeros and ones) with dimensions 400 by 500. I want to perform vertical and horizontal scans (that simply count how many zeros are to the left, right, top, bottom) through the matrix centered at a specific point.

Let's call my Matrix BW. I have an index such that BW(i,j). To find how many units are to the left, right, top, bottom I calculate these variables:

tothetop=i-1;
tothebottom=400-tothetop;
totheleft=j-1;
totheright=500-totheleft;

I tried to do a scan up and down from the point (i,j) with the following loops where TopCount & BotCount keep track of how many 0's are detected above and below the point at i,j:

    for p=1:1:tothetop
                   if BW(p,j)==0
                       TopCount=TopCount+1;
                   end
               end
    for q=tothebottom:1:rows
                   if BW(q,j)==0
                       BotCount=BotCount+1;
                   end
               end

However, I find that my counts are not accurate, namely, my scan downwards looks very similar to my scan upwards. If there is something wrong, I can't seem to figure it out, so please help!

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Aydin Akyol 2018-5-30

在 MATLAB Online 中打开

I think I'll just reverse my matrix (make all the 0's into 1 and vice versa) and then I was able to adapt the code used before to do what I wanted, with sum. So here is my scanning/summing code below:

    clear
  clc
  close all
xcenter = 3; 
ycenter = 3;
tmp = randi([0 1],5,5);
[rows,columns]=size(tmp);
left = sum(tmp((ycenter),(1:(xcenter-1)))); 
up = sum(tmp(1:ycenter-1,xcenter)); 
down = sum(tmp(ycenter+1:rows,xcenter));
right = sum(tmp((ycenter),(xcenter+1:columns)));
tmp
left
up
down
right