Calculate range of a variable

[Gobinda Natak]

Hi everyone

Not sure if I am getting old but imagine I have a data set of individuals i and time points j and a variable x like this:

clear
input i j x
1 1 -1
1 2  0
1 3  1
2 1  1
2 2  1
2 3  1
end

What's the best way to calculate the range of x within individuals i, like:

clear
input i j x x_range
1 1  0        2
1 2 -1        2
1 3  1        2
2 1  1        0
2 2  1        0
2 3  1        0
end

Sorry if this is trivial and thanks for your consideration

[Nick Cox]

The second method here works if and only if there are no missing values.

clear
input i j x
1 1 -1
1 2  0
1 3  1
2 1  1
2 2  1
2 3  1
end

bysort i : egen max = max(x)
by i: egen min = min(x)

gen range = max - min 

bysort i (x) : gen range2 = x[_N] - x[1]

list, sepby(i)

     +-----------------------------------------+
     | i   j    x   max   min   range   range2 |
     |-----------------------------------------|
  1. | 1   1   -1     1    -1       2        2 |
  2. | 1   2    0     1    -1       2        2 |
  3. | 1   3    1     1    -1       2        2 |
     |-----------------------------------------|
  4. | 2   1    1     1     1       0        0 |
  5. | 2   2    1     1     1       0        0 |
  6. | 2   3    1     1     1       0        0 |
     +-----------------------------------------+

[Gobinda Natak]

Thanks so much!