diamonds.py

import pandas as pd
from ggplot import diamonds

# 1) How do I easily create multiple summaries of multiple columns?
(
    diamonds
        .groupby('cut')
        .agg(??) # Equivalent of summarize(mean_x = mean(x),  var_xy = var(xy))
)


# 2) How do I easily put multiple summaries back into the original data frame?
(
    diamonds
        .groupby('cut')
        .?? # Equivalent of mutate(mean_x = mean(x),  var_xy = var(xy))?
)

# 3) Not a huge deal, but creating new columns with .assign is more verbose than mutate()
(
diamonds
    .assign(xy = lambda d: d.x + d.y, xz = lambda d: d.x + d.z)
)