#!/usr/bin/env python
# coding: utf-8

# # Line Charts
# 
# * [Simple line chart](#Simple-line-chart)
#     * [Data transform in Vega-Lite](#Data-transform-in-Vega-Lite)
#     * [Data transform in Pandas](#Data-transform-in-Pandas)
#     * [Log scale](#Log-scale)
# * [Grouped line chart](#Grouped-line-chart)
# * [Line chart with custom path](#Line-chart-with-custom-path)

# In[1]:


import altair as alt


# In[2]:


from vega_datasets import data
stocks = data.stocks()


# ## Simple line chart

# ### Data transform in Vega-Lite

# In[3]:


alt.Chart(stocks).mark_line().encode(
    x='date:T',
    y='price:Q'
).transform_filter("datum.symbol == 'GOOG'")


# ### Data transform in Pandas

# In[4]:


GOOG = stocks.query('symbol == "GOOG"')

alt.Chart(GOOG).mark_line().encode(
    x='date:T',
    y='price:Q'
)


# ### Log scale

# In[5]:


alt.Chart(GOOG).mark_line().encode(
    y=alt.Y('price:Q', scale=alt.Scale(type='log')),
    x='date:T',
)


# ## Grouped line chart

# In[6]:


alt.Chart(stocks).mark_line().encode(
    x='date:T',
    y='price',
    color='symbol',
)


# ## Line chart with custom path

# In[7]:


driving = data.driving()

alt.Chart(driving).mark_line().encode(
    alt.X('miles', scale=alt.Scale(zero=False)),
    alt.Y('gas', scale=alt.Scale(zero=False)),
    order='year:T',
)


# ## Layer points and lines with custom path

# In[8]:


base = alt.Chart(driving).encode(
    alt.X('miles', scale=alt.Scale(zero=False)),
    alt.Y('gas', scale=alt.Scale(zero=False)),
    order='year:T',
)

base.mark_line() + base.mark_point()