def z_score(data2d, axis=0):
    """Standarize the mean and variance of the data axis Parameters.

    :param data2d: DataFrame to normalize.
    :param axis: int, Which axis to normalize across. If 0, normalize across rows, 
                  if 1, normalize across columns.

    
    :Returns: Normalized DataFrame. Noramlized data with a mean of 0 and variance of 1 
              across the specified axis.

    """
    if axis == 1:
        z_scored = data2d
    else:
        z_scored = data2d.T

    z_scored = (z_scored - z_scored.mean()) / z_scored.std()

    if axis == 1:
        return z_scored
    else:
        return z_scored.T