# How do I plot Linear Regression?

Asked by At

I wish to learn how to use Plotly with Python for data analysis. I have been using this website as reference.

My current code looks like this:

``````from plotly import tools
import plotly as py
import plotly.graph_objs as go

py.offline.init_notebook_mode(connected=True)

# Create linear regression object
regr = linear_model.LinearRegression()

# Train the model using the training sets
regr.fit(X_train, y_train)

p1 = go.Scatter(x=X_test,
y=y_test,
mode='markers',
marker=dict(color='black')
)

p2 = go.Scatter(x=X_test,
y=regr.predict(X_test),
mode='lines',
line=dict(color='blue', width=3)
)

layout = go.Layout(xaxis=dict(ticks='', showticklabels=False,
zeroline=False),
yaxis=dict(ticks='', showticklabels=False,
zeroline=False),
showlegend=False, hovermode='closest')

fig = go.Figure(data=[p1, p2], layout=layout)

py.offline.iplot(fig)
``````

However, my output looks like

If I were to follow the website by every line, I would get this:

``````from plotly import tools
import plotly as py
import plotly.graph_objs as go

py.offline.init_notebook_mode(connected=True)

# Create linear regression object
regr = linear_model.LinearRegression()

# Train the model using the training sets
regr.fit(X_train, y_train)

def data_to_plotly(x):
k = []

for i in range(0, len(x)):
k.append(x[i][0])

return k

p1 = go.Scatter(x=data_to_plotly(X_test),
y=y_test,
mode='markers',
marker=dict(color='black')
)

p2 = go.Scatter(x=data_to_plotly(X_test),
y=regr.predict(X_test),
mode='lines',
line=dict(color='blue', width=3)
)

layout = go.Layout(xaxis=dict(ticks='', showticklabels=False,
zeroline=False),
yaxis=dict(ticks='', showticklabels=False,
zeroline=False),
showlegend=False, hovermode='closest')

fig = go.Figure(data=[p1, p2], layout=layout)

py.offline.iplot(fig)
``````

But it would generate the following error:

``````---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
~\Anaconda3\lib\site-packages\pandas\core\indexes\base.py in get_loc(self, key, method, tolerance)
2656             try:
-> 2657                 return self._engine.get_loc(key)
2658             except KeyError:

pandas/_libs/index.pyx in pandas._libs.index.IndexEngine.get_loc()

pandas/_libs/index.pyx in pandas._libs.index.IndexEngine.get_loc()

pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.PyObjectHashTable.get_item()

pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.PyObjectHashTable.get_item()

KeyError: 0

During handling of the above exception, another exception occurred:

KeyError                                  Traceback (most recent call last)
<ipython-input-84-5895927e91e2> in <module>
21     return k
22
---> 23 p1 = go.Scatter(x=data_to_plotly(X_test),
24                 y=y_test,
25                 mode='markers',

<ipython-input-84-5895927e91e2> in data_to_plotly(x)
17
18     for i in range(0, len(x)):
---> 19         k.append(x[i][0])
20
21     return k

~\Anaconda3\lib\site-packages\pandas\core\frame.py in __getitem__(self, key)
2925             if self.columns.nlevels > 1:
2926                 return self._getitem_multilevel(key)
-> 2927             indexer = self.columns.get_loc(key)
2928             if is_integer(indexer):
2929                 indexer = [indexer]

~\Anaconda3\lib\site-packages\pandas\core\indexes\base.py in get_loc(self, key, method, tolerance)
2657                 return self._engine.get_loc(key)
2658             except KeyError:
-> 2659                 return self._engine.get_loc(self._maybe_cast_indexer(key))
2660         indexer = self.get_indexer([key], method=method, tolerance=tolerance)
2661         if indexer.ndim > 1 or indexer.size > 1:

pandas/_libs/index.pyx in pandas._libs.index.IndexEngine.get_loc()

pandas/_libs/index.pyx in pandas._libs.index.IndexEngine.get_loc()

pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.PyObjectHashTable.get_item()

pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.PyObjectHashTable.get_item()

KeyError: 0

``````

I'm new to Plotly. How do I fix this?

EDIT: my X_test looks like this:

X_test

## 1 Answers

On

I see that `X_train` is a dataframe, Plotly is actually pretty friendly with Pandas, there are several examples in plotly's pandas example gallery so you don't have to deal with in between functions like `data_to_plotly` (that tutorial sadly looks quite outdated). In this case the scatters should look something like

``````p1 = go.Scatter(x=X_test['Explained by: GDP per capita'],
y=y_test, # Assuming y_test is a numpy array or pandas series
# if it is also a dataframe you have to specify the column
mode='markers',
marker=dict(color='black')
)

p2 = go.Scatter(x=X_test['Explained by: GDP per capita'],
y=regr.predict(X_test),
mode='lines',
line=dict(color='blue', width=3)
)
``````