REBIN:vector

1_example

 Suppose that X has 20 elements. After the command: REBIN X XOUT 2

        XOUT[1] = X[ 1] + X[ 2]
        XOUT[2] = X[ 3] + X[ 4]
        XOUT[3] = X[ 5] + X[ 6]
               ...
       XOUT[10] = X[19] + X[20]

2_example

 After the command:       REBIN [1:1000] X 3

   X[1] = 1+2+3
   X[2] = 4+5+6
   X[3] = 7+8+9
       ...
 X[333] = 997+998+999

 A warning will be given that length of [1:1000] is not evenly
 divisible by 3 and so the last bin is incomplete.