Generating NxN Matrix with Random 0s and 1s - MATLAB M File Help

[shawaj]

i am writing a MATLAB m file.

i need to generate a NxN matrix 25% filled with 0s and 1s in a random pattern...

is this at all possible?

also, in an NxN matrix, i need to select a 3x3 matrix centered around a certain point, can you help me out with this?

many thanks for your help

 

[cepheid]

also, in an NxN matrix, i need to select a 3x3 matrix centered around a certain point, can you help me out with this?

many thanks for your help

Isn't this just a question of indexing the array appropriately? I don't remember MATLAB syntax exactly, but often in these computational languages, indexing of an array is achieved by means of square brackets [] or parentheses (). So if your array is called 'arr' and the point of interest is at column i, row j (or vice versa, depending on the convention), you would index it as arr[i,j]. Now you just need to range from i-1 to i+1 and from j-1 to j+1. I don't remember what MATLAB uses to mean "range from", but it might be something like a:b to mean "range from a to b" with the colon replaced by whatever symbol MATLAB uses for this purpose. Then your 3x3 sub-array would be given by arr[i-1:i+1, j-1:j+1].

 

[shawaj]

I will try that out!

Any ideas on the other one? Generating a random matrix of 0s and 1s?

 

[shawaj]

many thanks for your help...cepheid

wasn't exactly what i was looking for but it helped me to find what i was looking for and have sorted that part of it now.

still trying to work out how to generate the random matrix as detailed above

 

[DeeNos]

I can confirm that it is possible to generate a NxN matrix with a random pattern of 0s and 1s using MATLAB. You can use the function "randi" to generate a random matrix with values between 0 and 1, and then use the "floor" function to round the values to either 0 or 1. For example, the code "A = floor(randi([0,1],N,N))" will generate a NxN matrix filled with random 0s and 1s.

To generate a matrix with a specific percentage of 0s and 1s, you can use the "rand" function to generate a matrix with values between 0 and 1, and then use the "round" function to round the values to either 0 or 1. For example, the code "A = round(rand(N,N)*0.25)" will generate a NxN matrix with 25% 1s and 75% 0s.

To select a 3x3 matrix centered around a certain point in a NxN matrix, you can use the "ceil" and "floor" functions to define the range of rows and columns, and then use the ":" operator to select the desired submatrix. For example, to select the 3x3 matrix centered around the point (i,j), the code would be "B = A(ceil(i-1.5):floor(i+1.5),ceil(j-1.5):floor(j+1.5))".

I hope this helps. Best of luck with your MATLAB m file!