helixmc.util.writhe_fuller¶

helixmc.util.writhe_fuller(dr, return_val_only=True)¶

Compute the writhe using the Fuller’s approximated single integral. Only guarantee to be correct modulo 4 pi. O(N) complexity.

Parameters:

dr : ndarray, shape = (N,3)

Input delta_r vectors (dr[i] = r[i+1] - r[i]).

return_val_only : bool, optional

If True, return one float value for the overall writhe of the system. Otherwise return the individual writhe contribution for each bp-step. Default set to True.

Returns:

writhe : float or ndarray of shape(N)

The overall writhe of the helix or the individual writhe contribution for each bp-step. See the ‘return_val_only’ parameter above.