How to do this

I have

R = input('Please enter a number of rows for the matrix');
C = input('Please enter a number of columns for the matrix');
M = randi(2, R, C);
M(M>1)=-1; 
M3 = M
M4=NaN(R+2,C+2) 
M4(2:end-1,2:end-1)=M3
c=zeros(R,C)
for i = 2:R+1
    for j=2:C+1
        arr = [M4(i-1,j) M4(i+1,j) M4(i,j+1) M4(i,j-1)]
        c(i-1,j-1)=nnz(ismember(arr,M4(i,j)))      
    end
end
 if -1 < c < 1
     if M3(:,:) > 0
         M3 = -1
     else M3(:,:) < 0
         M3 = 1
     end
 elseif 0 < c < 2

I need to:You will need to then determine the probability of spin change. Use that probabilities in the table given

based on:Neighbors with Similar Spin 1 2 3 4 5 Prob. 0.98 0.85 0.50 0.15 0.02

This means that if c = 0 100% chance that the element in the same position as c in M3 sill change from 1 to -1 or -1 to 1

if c = 1, a 98% chance it will change, 2 an 85% chance, 3 a 50% cahnce, 4 a 15% chance and 5 a 2% chance

how do i do this

[Stephen23]

-1 < c < 1

is unlikely to do what you want. You might like to read the MATLAB documentation (this is much more reliable than inventing syntaxes that don't exist):

https://www.mathworks.com/help/matlab/ref/lt.html

https://www.mathworks.com/help/matlab/matlab_prog/operator-precedence.html

Hint:

https://blogs.mathworks.com/loren/2012/05/14/why-is-answer-to-3-a-7-unexpected/

https://www.mathworks.com/matlabcentral/answers/258199-3-2-1-returns-logical-0

and many other threads on this forum. Testing things is also a good idea.

[Hunter Herrenkohl]

Actually that did work for what I am trying to do. I need to figure out the part after that.

[Jan]

@Hunter Herrenkohl: No, -1 < c < 1 cannot do, what you want. Did you read Stephen's comment?

-1 < c is either true or false, which is equivalent to 1 or 0. Afterwards you compare this 1 0r 0 by < 1. This is valid Matlab code, but a weird formulation. Do you mean this instead:

|-1 < c & c < 1|

?

Answer 1

[Jan]

You apply a comparison to a matrix and use it as condition to an if command. But if requires a scalar condition. Therefore Matlab inserts an all() implicitly. To be exact:

if all(condition(:)) && ~isempty(condition)

You want something else - at least I guess this.

cond1 = (-1 < c  & c < 1);  % Not -1 < c < 1 !!!
cond2 = M3 > 0;
cond3 = M3 < 0;
M3(cond1 & cond2) = -1;
M3(cond1 & cond3) =  1;