Copying/Replacing values from another variable

[Steven Ji]

Hi statalist,
I want to replace values of (month_2 * daylight_hours) with (month_1 * daylight_hours). For instance, instead of (11 to 20), it gives me values from (1 to 10). Is there any way to replace these values directly? Thanks in advance!

* Example generated by -dataex-. For more info, type help dataex
clear
input float(daylight_hours month_1 month_2 month_1Xhours month_2Xhours)
 1 1 0  1  0
 2 1 0  2  0
 3 1 0  3  0
 4 1 0  4  0
 5 1 0  5  0
 6 1 0  6  0
 7 1 0  7  0
 8 1 0  8  0
 9 1 0  9  0
10 1 0 10  0
11 0 1  0 11
12 0 1  0 12
13 0 1  0 13
14 0 1  0 14
15 0 1  0 15
16 0 1  0 16
17 0 1  0 17
18 0 1  0 18
19 0 1  0 19
20 0 1  0 20
end

[Øyvind Snilsberg]

maybe,

replace month_2Xhours = month_2Xhours - 10 if month_2

[Bruce Weaver]

Hello Steven Ji. I imagine there are many ways of doing what you asked. But they all seem rather ad hoc. I think it would be very helpful if you provided a bit more context. For example, if the first variable is indeed the number of daylight hours, and the values 11-20 are correct, why would you want a variable called month2Xhours to be equal to some value that is not month_2 * daylight_hours? This suggests to me some kind of problem with the way your data file is set up.

Cheers,
Bruce

[Steven Ji]

Hi @Bruce Weaver. Thank you for your reply.
Yes, they are indeed the number of daylight hours. This is not actual data, I just created a sample data here. Actually, we need to see the effect of month2Xhours if the daylight hours in month 2 are kept the same as in month 1.
I hope this answers your question. Let me know if you need more clarification. Thanks again!

[Bruce Weaver]

Thanks Steven. If the patter shown in the data sample you provided holds in the actual dataset, then I suppose you could use the mod() function to generate a new variable called m1hours. Something like this:

* Duplicate the data sample that was provided,
* but with shorter variable names!
clear
set obs 20
generate byte hours = _n
generate byte m1 = _n < 11
generate byte m2 = _n > 10
generate byte m1Xhours = m1*hours
generate byte m2Xhours = m2*hours

* In the example that was provided, m1hours can be obtained
* using the mod() function. But note that I have no idea
* if this will work in the actual dataset!

generate byte m1hours = mod(hours,10)
replace m1hours = 10 if m1hours==0
generate m2Xm1hours = m2*m1hours
list, clean ab(12)

Output:

. list, clean ab(12)  

       hours   m1   m2   m1Xhours   m2Xhours   m1hours   m2Xm1hours  
  1.       1    1    0          1          0         1            0  
  2.       2    1    0          2          0         2            0  
  3.       3    1    0          3          0         3            0  
  4.       4    1    0          4          0         4            0  
  5.       5    1    0          5          0         5            0  
  6.       6    1    0          6          0         6            0  
  7.       7    1    0          7          0         7            0  
  8.       8    1    0          8          0         8            0  
  9.       9    1    0          9          0         9            0  
 10.      10    1    0         10          0        10            0  
 11.      11    0    1          0         11         1            1  
 12.      12    0    1          0         12         2            2  
 13.      13    0    1          0         13         3            3  
 14.      14    0    1          0         14         4            4  
 15.      15    0    1          0         15         5            5  
 16.      16    0    1          0         16         6            6  
 17.      17    0    1          0         17         7            7  
 18.      18    0    1          0         18         8            8  
 19.      19    0    1          0         19         9            9  
 20.      20    0    1          0         20        10           10

But as I said in a comment line, I have no idea whether this will work as desired in your actual dataset.

[Steven Ji]

Hi @Bruce Weaver. Thank you so much!