options ls=80;

data surgical;
input x1 x2 x3 x4 y;
yp=log10(y);
cards;
   6.7  62   81  2.59  200  2.3010
   5.1  59   66  1.70  101  2.0043
   7.4  57   83  2.16  204  2.3096
   6.5  73   41  2.01  101  2.0043
   7.8  65  115  4.30  509  2.7067
   5.8  38   72  1.42   80  1.9031
   5.7  46   63  1.91   80  1.9031
   3.7  68   81  2.57  127  2.1038
   6.0  67   93  2.50  202  2.3054
   3.7  76   94  2.40  203  2.3075
   6.3  84   83  4.13  329  2.5172
   6.7  51   43  1.86   65  1.8129
   5.8  96  114  3.95  830  2.9191
   5.8  83   88  3.95  330  2.5185
   7.7  62   67  3.40  168  2.2253
   7.4  74   68  2.40  217  2.3365
   6.0  85   28  2.98   87  1.9395
   3.7  51   41  1.55   34  1.5315
   7.3  68   74  3.56  215  2.3324
   5.6  57   87  3.02  172  2.2355
   5.2  52   76  2.85  109  2.0374
   3.4  83   53  1.12  136  2.1335
   6.7  26   68  2.10   70  1.8451
   5.8  67   86  3.40  220  2.3424
   6.3  59  100  2.95  276  2.4409
   5.8  61   73  3.50  144  2.1584
   5.2  52   86  2.45  181  2.2577
  11.2  76   90  5.59  574  2.7589
   5.2  54   56  2.71   72  1.8573
   5.8  76   59  2.58  178  2.2504
   3.2  64   65  0.74   71  1.8513
   8.7  45   23  2.52   58  1.7634
   5.0  59   73  3.50  116  2.0645
   5.8  72   93  3.30  295  2.4698
   5.4  58   70  2.64  115  2.0607
   5.3  51   99  2.60  184  2.2648
   2.6  74   86  2.05  118  2.0719
   4.3   8  119  2.85  120  2.0792
   4.8  61   76  2.45  151  2.1790
   5.4  52   88  1.81  148  2.1703
   5.2  49   72  1.84   95  1.9777
   3.6  28   99  1.30   75  1.8751
   8.8  86   88  6.40  483  2.6840
   6.5  56   77  2.85  153  2.1847
   3.4  77   93  1.48  191  2.2810
   6.5  40   84  3.00  123  2.0899
   4.5  73  106  3.05  311  2.4928
   4.8  86  101  4.10  398  2.5999
   5.1  67   77  2.86  158  2.1987
   3.9  82  103  4.55  310  2.4914
   6.6  77   46  1.95  124  2.0934
   6.4  85   40  1.21  125  2.0969
   6.4  59   85  2.33  198  2.2967
   8.8  78   72  3.20  313  2.4955
;

proc reg data=surgical;
 model yp=x1-x4;

/* Partial residual plots 
   Note that the slope of the plot is equal to the coffficient extimate of
   the corrosponding parameter  of the full model
   This is an explanation.  In practice we use the partial option we used
   in the Surgical unit example 

     proc reg data=surgical;
        model yp=x1-x4/ partial;   
*/

proc reg data=surgical;
 model yp=x2-x4;
output out=b r=residyp;

proc reg data=b;
 model x1=x2 x3 x4;
output out=c r=residx1;

proc plot data=c;
 plot residyp*residx1;

proc reg data=c;
model residyp=residx1;

proc reg data=surgical;
 model yp=x1-x4/partial;

proc reg data=surgical;
 model yp=x1 x3 x4;;
output out=d r=residyp;

proc reg data=d;
 model x2=x1 x3 x4;
output out=d r=residx2;

proc plot data=d;
 plot residyp*residx2;    


proc reg data=d;
model residyp=residx2;

run;