def ENVP(df, pct=0.01, price='Close'):
    """
    Envelope Percent
    Returns: dict of lists of floats = jhta.ENVP(df, pct=.01, price='Close')
    Source: https://www.fmlabs.com/reference/default.htm?url=EnvelopePct.htm
    """
    envp_dict = {'hi': [], 'lo': []}
    for i in range(len(df[price])):
        hi = df[price][i] + df[price][i] * pct
        lo = df[price][i] - df[price][i] * pct
        envp_dict['hi'].append(hi)
        envp_dict['lo'].append(lo)
    return envp_dict
