Hello,
I'd like to repeat a linear regression model for groups of rows that are 
identified by an ID number.
My table is like this:
ID 	Y 	X1 	X2 	X3 	X4
1 	555 	111 	222 	333 	456
1 	345 	234 	445 	543 	33
1 	456 	353 	453 	456 	333
2 	562 	118 	229 	340 	463
2 	352 	241 	452 	550 	40
2 	463 	360 	460 	463 	340
3 	....
	...
	...
	...
	....
3 	
	
	
	
	
3 	
	
	
	
	


I want to obtain an estimate of the linear model for each ID.
ex.   y = a1X1 + b1X2 + c1X3 + d1X4     where ID= 1
         y = a2X1 + b2X2 + c2X3 + d2X4    where ID= 2        and so on...

I'd like to obtain a table such this:

ID 	a 	b 	c 	d
1 	... 	... 	... 	..
2 	.. 	.. 	.. 	..
3 	.. 	.. 	.. 	..



Can you sugget me something?
Can I use a "for" script?
Thank you very much!
Valeria

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