How to randomly generate 0.1 or -0.1?

Hello. Good day. I have this code:

        for sm=0:0.1:0.1                                                                                       
             f=sm*eye(N)                                    
        end

I get the following: f =

     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0

f =

    0.1000         0         0         0         0         0         0         0         0         0
         0    0.1000         0         0         0         0         0         0         0         0
         0         0    0.1000         0         0         0         0         0         0         0
         0         0         0    0.1000         0         0         0         0         0         0
         0         0         0         0    0.1000         0         0         0         0         0
         0         0         0         0         0    0.1000         0         0         0         0
         0         0         0         0         0         0    0.1000         0         0         0
         0         0         0         0         0         0         0    0.1000         0         0
         0         0         0         0         0         0         0         0    0.1000         0
         0         0         0         0         0         0         0         0         0    0.1000

I want to obtain the following: f =

     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0

f =

    -0.1000         0         0         0         0         0         0         0         0         0
         0    0.1000         0         0         0         0         0         0         0         0
         0         0    -0.1000         0         0         0         0         0         0         0
         0         0         0    -0.1000         0         0         0         0         0         0
         0         0         0         0    0.1000         0         0         0         0         0
         0         0         0         0         0    0.1000         0         0         0         0
         0         0         0         0         0         0    0.1000         0         0         0
         0         0         0         0         0         0         0    -0.1000         0         0
         0         0         0         0         0         0         0         0    0.1000         0
         0         0         0         0         0         0         0         0         0    -0.1000

As we can see, we generated 0.1 and -0.1 randomly. That's what I want randomly generated 0.1 and -0.1 I hope I have explained my question well. Greetings and thanks.

Answer 1

[Stephen23]

diag((2*randi(0:1,1,N)-1)/10)

[Ricardo Gutierrez]

Excellent!!!!!!! Thank you very much

[Ricardo Gutierrez]

Hi. Using this code that you did how to previously generate the matrix:

     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0

and then the random matrix (0.1 or -0.1)

    0.1000         0         0         0         0         0         0         0         0         0
         0    0.1000         0         0         0         0         0         0         0         0
         0         0    -0.1000         0         0         0         0         0         0         0
         0         0         0    0.1000         0         0         0         0         0         0
         0         0         0         0    -0.1000         0         0         0         0         0
         0         0         0         0         0    0.1000         0         0         0         0
         0         0         0         0         0         0    0.1000         0         0         0
         0         0         0         0         0         0         0    0.1000         0         0
         0         0         0         0         0         0         0         0    -0.1000         0
         0         0         0         0         0         0         0         0         0    -0.1000

[Stephen23]

" Using this code that you did how to previously generate the matrix... and then the random matrix (0.1 or -0.1)"

It really works the other way around: first it generates a vector of random values, and then uses diag to form a matrix, placing those values along the diagonal. I am sure that you can read the randi and diag help to know what they do, and try the parts of the code yourself:

>> N = 6;
>> randi(0:1,1,N)
ans =
     1     0     1     0     0     0
>> (2*randi(0:1,1,N)-1)/10
ans =
          0.1          0.1         -0.1         -0.1         -0.1          0.1
>> diag((2*randi(0:1,1,N)-1)/10)
ans =
          0.1            0            0            0            0            0
            0          0.1            0            0            0            0
            0            0         -0.1            0            0            0
            0            0            0          0.1            0            0
            0            0            0            0          0.1            0
            0            0            0            0            0         -0.1

[Ricardo Gutierrez]

It is understood. Thank you very much