def categorize(x, upper=0.05, lower=-0.05):
    """
    Categorizes tweets into sentiment categories of 0, 2 and 4.
    Negative, Netral and Postive, respectively.
    The upper and lower variables are standard thresholds from VADER Sentiment
    """
    if x < lower:
        return 0
    elif ((x > (lower+0.0001) and x < upper)):
        return 2
    else:
        return 4