Dear statalist forum members,
For the below sample data, I would like to subtract X1 from X5 and save it as X13. Likewise, I would like to subtract X2 from X6 and save it as X14. IK have tried the below loop but it does not work. Thanks for your help.
NM

Code:
forval i = 1/8 {

gen X`i+12'=X`i'-X`i+4'
}


Code:
* Example generated by -dataex-. For more info, type help dataex
clear
input float(X1 X2 X3 X4 X5 X6 X7 X8 X9 X10 X11 X12)
22.573143 7.601128  30.17427 .7480924 16.524061 9.962753 26.486814 .6238599 21.069393 14.272256  35.34165 .5961633
 21.19807 7.195382  28.39345 .7465831   15.5447 9.462714 25.007414 .6216037 19.923904  13.46682 33.390724 .5966898
19.824026 6.810086  26.63411 .7443097 14.550502 8.996266  23.54677 .6179405 18.765072  12.68481  31.44988 .5966659
18.467472 6.435489  24.90296 .7415773 13.565183 8.549612 22.114796 .6133985  17.60442 11.917387 29.521807 .5963192
 17.13954 6.066377  23.20592 .7385849 12.603266 8.115009 20.718275 .6083164  16.45005 11.159567  27.60962 .5958087
15.848076 5.700288 21.548365 .7354653  11.67356 7.688297 19.361856 .6029153  15.30798 10.408947 25.716927 .5952492
end