def where_cross(data,threshold):
    """return a list of Is where the data first crosses above threshold."""
    Is=np.where(data>threshold)[0]
    Is=np.concatenate(([0],Is))
    Ds=Is[:-1]-Is[1:]+1
    return Is[np.where(Ds)[0]+1]
def where_cross(data,threshold):
    """return a list of Is where the data first crosses above threshold."""
    Is=np.where(data>threshold)[0]
    Is=np.concatenate(([0],Is))
    Ds=Is[:-1]-Is[1:]+1
    return Is[np.where(Ds)[0]+1]
return a list of Is where the data first crosses above threshold.