trying to change negative values to 0 and positive to 1

• i want to change all the positive number in voltsadd matrix to 1 and negative to 0
• I am using a(a<0) = 0 command but its not working
• here is the sample of my code

• voltsadd_val = volts_add;
• voltsadd_val(voltsadd_val<0) = 0;
• voltsadd_val(voltsadd_val>0) = 1;

in the image below 12 bit is negative but its not working properly it always shows 1 as the output. Kindly help i dont understand where am i going wrong

Answer 1

[per isakson]

The problem is somewhere else

>> volts_add = randn(1,6);
>> volts_add( volts_add <= 0 ) = 0
volts_add =
    0.5377    1.8339         0    0.8622    0.3188         0

See: Debug a MATLAB Program and Examine Values While Debugging