data exm10_1;
input x1 x2 x3 y;
cards;
51.3 73.6 36.4 2.99
48.9 83.9 34.0 3.11
42.8 78.3 31.0 1.91
55.0 77.1 31.0 2.63
45.3 81.7 30.0 2.86
45.3 74.8 32.0 1.91
51.4 73.7 36.5 2.98
53.8 79.4 37.0 3.28
49.0 72.6 30.1 2.52
53.9 79.5 37.1 3.27
48.8 83.8 33.9 3.10
52.6 88.4 38.0 3.28
42.7 78.2 30.9 1.92
52.5 88.3 38.1 3.27
55.1 77.2 31.1 2.64
45.2 81.6 30.2 2.85
51.4 78.3 36.5 3.16
48.7 72.5 30.0 2.51
51.3 78.2 36.4 3.15
45.2 74.7 32.1 1.92
;
proc reg;
model y=x1 x2 x3/tol vif collin selection=stepwise r;
run;
请教一下，关于多元线性回归中的tol vif collin selection=stepwise r是什么意思呢？