In this lab we will build out functions to help us plot visualizations in lessons going forward.
Let's start by providing a function called plot
which plots our data.
import plotly
from plotly.offline import iplot, init_notebook_mode
init_notebook_mode(connected=True)
def plot(figure):
plotly.offline.iplot(figure)
To see our plot on the screen, we provide our plot
function a dictionary. The dictionary has a key of data
which points to a list of traces. Let's see it!
sample_trace = {'x': [1, 2, 3], 'y': [2, 3, 4]}
other_sample_trace = {'x': [2, 3, 4], 'y': [5, 3, 4]}
sample_figure = {'data': [sample_trace, other_sample_trace], 'layout': {'title': 'Our sample plot'}}
plot(sample_figure)
Ok, now that our plot
function works, we need an easy way to create the following:
- traces
- figures
- layouts
Let's take these one by one. We'll start with a build_trace
function that easily creates traces.
Write a build_trace
function that can take in data that comes in the following format:
data = [{'x': 1, 'y': 1}, {'x': 3, 'y': 2}, {'x': 2, 'y': 5}]
And returns data like the commented out dictionary below:
data = [{'x': 1, 'y': 1}, {'x': 3, 'y': 2}, {'x': 2, 'y': 5}]
build_trace(data)
# {'mode': 'markers', 'name': 'data', 'x': [1, 3, 2], 'y': [1, 2, 5]}
So build_trace
that takes in a list of data points as arguments and returns a dictionary with a key of x
that points to a list of x values, and a key of y
that points to a list of y values.
Note: Look at the parameters provided for
build_trace
. The argumentsmode = 'markers'
andname = 'data'
may seem scary since we haven't seem them before. No need to worry! These are default arguments.
If no argument for
mode
orname
is provided when we call thebuild_trace
function, Python will automatically set these parameters to the value provided, which, in this case would be 'markers' for the mode and 'data' for the name.
def build_trace(data, mode = 'markers', name = 'data'):
pass
So by default, if we just call build_trace(data)
without specifying either a mode or a name, the function will automatically set these parameters to 'markers' and 'data' respectively.
data = [{'x': 1, 'y': 1}, {'x': 3, 'y': 2}, {'x': 2, 'y': 5}]
build_trace(data)
# {'mode': 'markers', 'name': 'data', 'x': [1, 3, 2], 'y': [1, 2, 5]}
If we want our build_trace
function to take a different mode arguement, we add a second argument when we call the function which will overwrite the mode's default argument.
build_trace(data, 'scatter')
# {'mode': 'scatter', 'name': 'data', 'x': [1, 3, 2], 'y': [1, 2, 5]}
We could do the same thing with the name of the plot. This is useful for when we have more than one trace in the same plot.
Order matters. The value passed through as the
name
argument, should correspond to the value of thename
key in our returned dictionary.
build_trace(data, 'markers', 'sample plot')
# {'mode': 'markers', 'name': 'sample plot', 'x': [1, 3, 2], 'y': [1, 2, 5]}
# trace0 = build_trace(data)
# trace0 = build_trace(data, 'markers')
# trace1 = build_trace(data, 'lines', 'my_trace')
# plot({'data':[trace0, trace1]})
Now let's write another function to create a trace called trace_values
. It works just like our build_trace
function, except that it takes in a list of x_values and a list of y_values and returns our trace dictionary. We will use default argument again here in the same manner as before.
def trace_values(x_values, y_values, mode = 'markers', name="data"):
pass
trace_values([1, 2, 3], [2, 4, 5])
# {'mode': 'markers', 'name': 'data', 'x': [1, 2, 3], 'y': [2, 4, 5]}
Now let's try to build a line trace with our newly defined trace_values
function. We will set mode
to 'lines' and the name
of our trace to 'line trace'.
trace_values([1, 2, 3], [2, 4, 5], 'lines', 'line trace')
# {'mode': 'lines', 'name': 'line trace', 'x': [1, 2, 3], 'y': [2, 4, 5]}
From there, we can use our trace_values
function to plot our chart.
Uncomment and run the code below
# trace2 = trace_values([1, 2, 3], [2, 4, 5], 'lines', 'line trace')
# plot({'data': [trace2]})
Ok, now that we have built some functions to create traces, let's write a function to create a layout. Remember that our layout also can be passed to our plot function.
Uncomment and run the code below.
# plot({'data': [trace0, trace2], 'layout': {'title': 'Sample Title'}})
Our layout
function should return a dictionary, just as it's defined in the above plot. We'll start by returning an empty dictionary then below we'll walk through building out the rest of the function.
def layout(x_range = None, y_range = None, options = {}):
pass
layout()
# {}
Oftentimes in building a layout, we want an easy way to set the range for the x
and y
axis. To set a range in the x-axis of
{'xaxis': {'range': [1, 4]}, 'yaxis': {'range': [2, 5]}}
Let's start with adding functionality to the layout()
function so it can set the range for the x-axis. (Hint: Google search Python's built-in isinstance()
and update()
functions.)
Add an argument of x_range returns a dictionary with a range set on the xaxis.
layout([1, 4])
# {'xaxis': {'range': [1, 4]}}
We want to ensure that when an x_range is not provided, an empty dictionary is still returned.
layout()
# {}
The x_range
should be a default argument that sets x_range
to None
. Then, only add a key of xaxis to the dictionary layout when the x_range
does not equal None
.
layout() # {}
Now let's provide the same functionality for the y_range
. When the y_range
is provided we add a key of yaxis
which points to a dictionary that expresses the y-axis range.
layout([1, 3], [4, 5])
# {'xaxis': {'range': [1, 3]}, 'yaxis': {'range': [4, 5]}}
Now have the final argument of our layout function be options. The options
argument should by default point to a dictionary. And whatever is provided as pointing to the options argument should be updated into the returned dictionary.
layout(options = {'title': 'foo'})
layout([1, 3], options = {'title': 'chart'})
# {'title': 'chart', 'xaxis': {'range': [1, 3]}}
Ok, now let's see this layout
function in action.
another_trace = trace_values([1, 2, 3], [6, 3, 1])
another_layout = layout([-1, 4], [0, 7], {'title': 'Going Down...'})
# plot({'data': [another_trace], 'layout': another_layout})
Finally, we'll modify the plot
function for you so that it takes the data, and the layout as arguments.
def plot(traces = [], layout = {}):
if not isinstance(traces, list): raise TypeError('first argument must be a list. Instead is', traces)
if not isinstance(layout, dict): raise TypeError('second argument must be a dict. Instead is', layout)
plotly.offline.iplot({'data': traces, 'layout': layout})
Uncomment the below code to see the updated plot
function in action.
trace4 = trace_values([4, 5, 6], [10, 5, 1], mode = 'lines')
last_layout = layout(options = {'title': 'The big picture'})
plot([trace4], last_layout)
In this lab, we built out some methods so that we can easily create graphs going forward. We'll make good use of them in the lessons to come, as well as write new methods to help us easily display information in our charts.