Problem in calculation formula

2017 4 4
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更新时间：2017 4 5
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Hi, this my problem. "Subscript indices must either be real positive integers or logicals. Error in tryMVM (line23) s=sum(y(X-i,Y-j)-mean)". X and Y is my point. How can i convert double to logical?

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KSSV
KSSV 2017-4-4
Show us the full code......we cannot help unless full code is known.
Syakira Akmal
Syakira Akmal 2017-4-5
this is my coding..
a = imread('snake4.JPG');
imshow(a);
x = roipoly(a);
figure, imshow(x);
y = imresize(x,0.5);
figure, imshow(y);
imwrite(y,'s1.jpg');
%to set point
[X,Y] = meshgrid(1:1224,1:1224);
%to calculate mean image
b = imread('s1.jpg');
m = mean2(b)
%to calculate standard deviation
c = imread('s1.jpg');
sd = std2(c)
%mean-variance moving window operation
for i=1:1224
for j=1:1224
s=sum(y(X-i,Y-j)-m) %problem
end

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Guillaume
Guillaume 2017-4-4

0 个投票

The problem you have is not that your subscripts are not logical, it is that either they're not positive or they're not integers. I'm fairly certain, even with the very limited info you've provided, that converting to logical won't give you the result you want.
So,
  • make sure that X, Y, i and j are integers
  • make sure that X > i and Y > j
  • and, you never know, make sure that you haven't got a variable called sum that stops you from using the sum function.
And on that last point, don't use mean as a variable name since it prevents you from using the mean function.

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Syakira Akmal
Syakira Akmal 2017-4-5
this is my coding..
a = imread('snake4.JPG');
imshow(a);
x = roipoly(a);
figure, imshow(x);
y = imresize(x,0.5);
figure, imshow(y);
imwrite(y,'s1.jpg');
%to set point
[X,Y] = meshgrid(1:1224,1:1224);
%to calculate mean image
b = imread('s1.jpg');
m = mean2(b)
%to calculate standard deviation
c = imread('s1.jpg');
sd = std2(c)
%mean-variance moving window operation
for i=1:1224
for j=1:1224
s=sum(y(X-i,Y-j)-m) %problem
end
I still cannot solve the problem...
Guillaume
Guillaume 2017-4-5
Well, yes that code is not going to work. X(1) is 1, so for any i, the expression X-i is always going to result in at least one value less than 1. When i is 1224, none of the values in X-i are valid indices.
In any case, nothing in that loop makes sense and I've no idea what you're trying to achieve. If you're trying to find the mean of the image over a moving window then you can use conv2:
%mean of image over sliding window of size mxn:
conv2(img, ones(m, n)/(m*n))

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