data in; input RUN PH TEMP CONC P_RATIO @@;
cards;
 16    4.0     35       50   0.04716     3    4.0     35      500   0.07468
  8    4.0     55      275   0.07734     4    4.0     75       50   0.09528
 15    4.0     75      500   0.07521    11    5.5     35      275   0.00810
 17    5.5     55       50   0.02182     1    5.5     55      275   0.01673
  9    5.5     55      275    .         10    5.5     55      275   0.01169
 18    5.5     55      275   0.00805     5    5.5     55      500   0.01131
  7    5.5     75      275   0.00987     6    7.0     35       50   0.00000
 14    7.0     35      500   0.00127    13    7.0     55      275   0.00234
 12    7.0     75       50   0.01912     2    7.0     75      500   0.00279
 20    4.0     35       50   0.05598    30    4.0     35      500   0.05096
 31    4.0     55      275   0.10859    32    4.0     75       50   0.03127
 24    4.0     75      500   0.05732    25    5.5     35      275   0.00704
 23    5.5     55       50   0.00913    19    5.5     55      275   0.00795
 27    5.5     55      275   0.01290    28    5.5     55      275   0.00723
 36    5.5     55      275   0.00718    35    5.5     55      500   0.01045
 29    5.5     75      275   0.00677    33    7.0     35       50   0.00000
 22    7.0     35      500   0.00090    26    7.0     55      275   0.00150
 21    7.0     75       50   0.01486    34    7.0     75      500   0.00112
;
PROC RSREG DATA=IN;
    MODEL P_RATIO = PH TEMP CONC / LACKFIT ;
    RIDGE MAX MIN OUTR=RDG RADIUS=0 TO 1.7 BY .1;
TITLE H=.8CM F=SWISS 'RIDGE ANALYSIS USING RSREG';

DATA RDG (DROP=_PRED_); SET RDG;
     IF _TYPE_='MINIMUM' THEN PMIN = _PRED_; 
     IF _TYPE_='MAXIMUM' THEN PMAX = _PRED_;  

SYMBOL1 INTERPOL=SPLINE VALUE=CIRCLE;
PROC GPLOT DATA=RDG;
     PLOT PMIN*_RADIUS_=1 PMAX*_RADIUS_=2 / OVERLAY;
LABEL _PRED_='RIDGE VALUE';

DATA RDG; SET RDG;
PH = (PH-5.5)/1.5;   TEMP = (TEMP-55)/20;  CONC = (CONC-275)/225;

PROC SORT DATA=RDG; BY _TYPE_; 
PROC GPLOT DATA=RDG; BY _TYPE_;
     PLOT PH*_RADIUS_='P'
          TEMP*_RADIUS_='T'
          CONC*_RADIUS_='C' / OVERLAY VREF=0 ;
TITLE H=.8CM F=SWISS 'CODED RIDGE COORDINATES';
RUN;