void curvefollow (srow, scol, x, y, npts) CURSOR.C Level 3
int srow scol The row and column of the digital readout on the screen. (0, 0) is at the top left
float *x, *y The coordinate vectors for the curve to be followed.
int npts The number of points in the coordinate vectors.
curvefollow() displays a digital readout on the screen at the location srow, scol in an 8 ´ 10 pixel font and the cross hairs are displayed. Using the left and right arrow keys, you can move the cross hairs from point to point on the 
curve given by x and y (or r and theta for polar plots). The <Home> and <End> keys may be used to move the cursor to the start and end of the curve. Points may be marked and unmarked with the <Ins> and <Del> keys, but nothing is entered into the TKF file. The mode is exited by pressing the <Esc> key.

This mode allows visual selection and readout of the points along the curve. In contrast to the curson() functions, 
the displayed values for x and y are taken directly from the input vectors, and hence are not subject to the roundoff 
and discretization errors that occur if the screen point is converted to user units.