Programming and Graphics

9.4 Transferring data to theMatlabdomain 305

//--- Matlab session:

engEvalString(cokar, "Handle1 = plot(xx,yy,’-’,’linewidth’,2);");

engEvalString(cokar, "hold on");

engEvalString(cokar, "axis square");

engEvalString(cokar, "axis([-5 5 -5 5])");

engEvalString(cokar, "set(Handle1,’EraseMode’,’xor’);");

engEvalString(cokar, "xlabel(’x’,’fontsize’,15)");

engEvalString(cokar, "ylabel(’y’,’fontsize’,15)");

engEvalString(cokar, "set(gca,’fontsize’,15)");

//--- Animation:

float velx=1.0;

float vely=0.5;

float Dt = 0.1; // time step

//--- Loop over time:

for (int istep=0; istep<=10000; istep++)

{

centerx = centerx+velx*Dt;

centery = centery+vely*Dt;

for (int i=0; i<=N; i++)

{

x[i]=x[i]+velx*Dt;

y[i]=y[i]+vely*Dt;

}

memcpy((void *)mxGetPr(xx), (void *)x, sizeof(x));

engPutVariable(cokar, "xx", xx);

memcpy((void *)mxGetPr(yy), (void *)y, sizeof(y));

engPutVariable(cokar, "yy", yy);

engEvalString(cokar, "set(Handle1,’XData’,xx,’YData’,yy);");

engEvalString(cokar, "drawnow;");

if(centerx > 5.0) velx=-velx; //--- reflect if necessary

if(centerx <-5.0) velx=-velx;

if(centery > 5.0) vely=-vely;

if(centery <-5.0) vely=-vely;

}

//--- End the session: