drawing sine wave using opencv

I want to draw a sine wave on a image using openCV. I developed the following code, but the output is not coming as expected:

#include "opencv2/imgproc/imgproc.hpp"
 #include "opencv2/highgui/highgui.hpp"
 #include <stdlib.h>
 #include <stdio.h>
 #include <math.h>
 #include "opencv/cv.h"
 #include "opencv/highgui.h"
 void main()
 { 
 double y[100]; 
       float x; 
 
 
   for(x=0;x<100;x++)
   {
       y[(int)floor(x)]=sin(x);
 
   }
 
   IplImage *grf = cvCreateImage( cvSize( 200, 200), IPL_DEPTH_8U, 1 );
 
 
   for(int x=0;x<100;x++)
   {
   cvLine(grf ,                         /* the dest image */
           cvPoint(x, y[x]),  /* start point */
 
            cvPoint(x+1, y[x+1]),            /* end point */
            CV_RGB(255, 0, 0),      /* the color; green */
            2, 4, 0);                    /* thickness, line type, shift */
 
   }
 
 
   cvNamedWindow("img", CV_WINDOW_AUTOSIZE);
     cvShowImage("img", grf);
     cvWaitKey(0);
     cvDestroyWindow("img");
     cvReleaseImage(&grf);
 }
 

I have verified the values coming in y array is correct, and plotted these y values using MATLAB. The MATLAB plot is coming a sine wave. Can you tell me why i am not getting correct plot using above code.

My output plot of sine wave is coming as below: you can see I am just getting a horizontal line instead of the sine wave. Any help regarding this?

---