I've got some baseball stats, RBIs by season, let's say:
player s1 s2 s3 Brian_Giles 66 68 70 Joe_Thomas 71 72 71 Robin_Yount 71 69 68 Jim_Jones 66 66 65
And I want to do a simple linear regression using lm() on this data to predict their RBI #s in a 4th season. Would I need another variable here to create my formula? How would I most simply complete this linear regression?
I'm trying to work off of this tutorial (http://www.r-bloggers.com/wp-content/uploads/2009/11/simpleLinRegExample1.txt), which seems like I might need a second variable, (I'm new to linear regressions, obviously) but I can't figure out what it should be. The slope of a best-fit line for those three seasons of data?