options fullstimer;proc iml;    reset deflib=sashelp;    use class;    read all var {weight height} into me;    m = nrow(me);    *scaling feature;    s1 = max(me[,1])-min(me[,1]);    s2 = max(me[,2])-min(me[,2]);    mean_s1 = mean(me[,1]);    mean_s2 = mean(me[,2]);    me[,1] = (me[,1]-mean_s1)/s1;    me[,2] = (me[,2]-mean_s2)/s2;    *scaling feature;    *print me;    theta_0 = 0;    theta_1 = 0;    x0 = 1;    ov = 10;    alpha = 0.03;    *print me;    rec = 0;
　　    do while (ov>0.000000001);     theta_0Old = theta_0;    theta_1Old = theta_1;    *compute old residual and collect data to plot r*numOfIteration;    rec = rec + 1;    r2 = 0;    do i=1 to m;            residual_tt =(theta_0Old*x0 + theta_1Old*me[i,2]) - me[i,1];            r2 = r2+residual_tt*residual_tt;    end;    Jtheta = r2/2/m;    xy = xy//(rec||Jtheta);    *compute old residual and collect data to plot r*numOfIteration;        res = 0; res_1 = 0;        do i=1 to m;            residual_0 =(theta_0Old*x0 + theta_1Old*me[i,2]) - me[i,1];            res = res + (residual_0*x0);            res_1 = res_1 + (residual_0*me[i,2]);        end;        *print residual_0;        theta_0 = theta_0Old - alpha*res/m;        theta_1 = theta_1Old - alpha*res_1/m;    *update residual and decide whether it‘s convergence;        r2 = 0;        do i=1 to m;            residual_tt =(theta_0*x0 + theta_1*me[i,2]) - me[i,1];            r2 = r2+residual_tt*residual_tt;        end;        Jtheta_new = r2/2/m;        ov = abs(Jtheta_new - Jtheta);    *update residual and decide whether it‘s convergence;        end;    print ov;    call pgraf(xy,‘*‘,‘x‘,‘y‘,‘mmmmm‘);    theta_0_last = theta_0*s1+mean_s1-mean_s2*s1*theta_1/s2;    theta_1_last = theta_1*s1/s2;    print theta_0_last theta_1_last;    run;quit;