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error in resultes of "OR" operator

Asked by Aseel H on 29 Jun 2013

in the following code I need subtract the values 255 and 254 by 1

and adding the value 0 and 1 by 1 and the other values don't change

    X=[255 250 0 100 38 47 150 254
       253 251 250 0 0 47 25 252
       0 0 0 90 145 74 30 249
        200 220 0 1 2 3 225 4
       0 255 251 0 4 20 35 245
       255 250 0 100 38 47 150 254
       200 220 0 1 2 3 225 4
       253 251 250 0 0 47 25 252];
    Max = 255;
    Min = 0;
    [x,y] = size(X);
    for i= 1:x
        for j = 1:y
            if X(i,j)==(Max | Max-1)
                X1(i,j) = X(i,j)-1;
            elseif X(i,j)== (Min | Min+1) 
                X1(i,j) = X(i,j)+1;
            else
                X1(i,j)= X(i,j);
            end
        end
    end

**************************************

but resultes not change:it give me

    X1=[255 250 0 100 38 47 150 254
       253 251 250 0 0 47 25 252
       0 0 0 90 145 74 30 249
        200 220 0 1 2 3 225 4
       0 255 251 0 4 20 35 245
       255 250 0 100 38 47 150 254
       200 220 0 1 2 3 225 4
       253 251 250 0 0 47 25 252];

Please....I need know what error in the code

0 Comments

Aseel H

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2 Answers

Answer by the cyclist on 29 Jun 2013
Accepted answer

You have a syntax problem when you try to do

X(i,j)==(Max | Max-1)

because that is not going to check whether X(i,j) is in a set. That is valid MATLAB syntax, but it is not doing what you think it is. You might want to read the documentation for the or() function to see exactly what it does:

doc or

Instead, I think you want the syntax

if (X(i,j)==Max) | (X(i,j)==(Max-1))

You could also use

if ismember(X(i,j),[Max Max-1])

Finally, note that you can do this operation on the entire matrix at once:

X1 = X;
idxHi = ismember(X,[255,254])
X1(idxHi) = X(idxHi)-1;
idxLo = ismember(X,[0,1])
X1(idxLo) = X(idxLo)+1;

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the cyclist
Answer by Walter Roberson on 29 Jun 2013
X(i,j)== (Min | Min+1)

means to evaluate the logical condition (Min | Min+1) and then compare that logical result to what is in X(i,j).

Try

if X(i,j) == Min | X(i,j) == Min+1

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Walter Roberson

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