def returns_from_prices(prices):
    """
    Calculate the returns given prices.

    :param prices: adjusted (daily) closing prices of the asset, each row is a
                   date and each column is a ticker/id.
    :type prices: pd.DataFrame
    :return: (daily) returns
    :rtype: pd.DataFrame
    """
    return prices.pct_change().dropna(how='all')
