Box Plot using Plotly in Python
Plotly is a Python library which is used to design graphs, especially interactive graphs. It can plot various graphs and charts like histogram, barplot, boxplot, spreadplot and many more. It is mainly used in data analysis as well as financial analysis. plotly is an interactive visualization library.
Box Plot
A box plot is a demographic representation of numerical data through their quartiles. The end and upper quartiles are represented in box, while the median (second quartile) is notable by a line inside the box. Plotly.express is convenient,high-ranked interface to plotly which operates on variety of data and produce a easy-to-style figure.Box are much beneficial for comparing the groups of data. Box plot divide approx. 25% of section data into sets which helps ion quickly identifying values, the dispersion of the data set, and signs of skewness.
Syntax: plotly.express.box(data_frame=None, x=None, y=None, color=None, facet_row=None, facet_col=None, facet_col_wrap=0, hover_name=None, hover_data=None, custom_data=None, animation_frame=None, animation_group=None, category_orders={}, labels={}, color_discrete_sequence=None, color_discrete_map={}, orientation=None, boxmode=None, log_x=False, log_y=False, range_x=None, range_y=None, points=None, notched=False, title=None, template=None, width=None, height=None)
Parameters:
| Name | Description |
|---|---|
| data_frame | This argument needs to be passed for column names (and not keyword names) to be used. Array-like and dict are transformed internally to a pandas DataFrame. Optional: if missing, a DataFrame gets constructed under the hood using the other arguments. |
| x | Either a name of a column in data_frame, or a pandas Series or array_like object. Values from this column or array_like are used to position marks along the x axis in cartesian coordinates. Either x or y can optionally be a list of column references or array_likes, in which case the data will be treated as if it were ‘wide’ rather than ‘long’. |
| y | Either a name of a column in data_frame, or a pandas Series or array_like object. Values from this column or array_like are used to position marks along the y axis in cartesian coordinates. Either x or y can optionally be a list of column references or array_likes, in which case the data will be treated as if it were ‘wide’ rather than ‘long’. |
| color | Either a name of a column in data_frame, or a pandas Series or array_like object. Values from this column or array_like are used to assign color to marks. |
| facet_row | Either a name of a column in data_frame, or a pandas Series or array_like object. Values from this column or array_like are used to assign marks to facetted subplots in the vertical direction. |
| facet_col | Either a name of a column in data_frame, or a pandas Series or array_like object. Values from this column or array_like are used to assign marks to facetted subplots in the horizontal direction. |
| facet_col_wrap | Maximum number of facet columns. Wraps the column variable at this width, so that the column facets span multiple rows. Ignored if 0, and forced to 0 if facet_row or a marginal is set. |
| hover_name | Either a name of a column in data_frame, or a pandas Series or array_like object. Values from this column or array_like appear in bold in the hover tooltip. |
| hover_data | Either a list of names of columns in data_frame, or pandas Series, or array_like objects or a dict with column names as keys, with values True (for default formatting) False (in order to remove this column from hover information), or a formatting string, for example ‘:.3f’ or ‘|%a’ or list-like data to appear in the hover tooltip or tuples with a bool or formatting string as first element, and list-like data to appear in hover as second element Values from these columns appear as extra data in the hover tooltip. |
| custom_data | Either names of columns in data_frame, or pandas Series, or array_like objects Values from these columns are extra data, to be used in widgets or Dash callbacks for example. This data is not user-visible but is included in events emitted by the figure (lasso selection etc.) |
| animation_frame | Either a name of a column in data_frame, or a pandas Series or array_like object. Values from this column or array_like are used to assign marks to animation frames. |
| animation_group | Either a name of a column in data_frame, or a pandas Series or array_like object. Values from this column or array_like are used to provide object-constancy across animation frames: rows with matching `animation_group`s will be treated as if they describe the same object in each frame. |
| category_orders | By default, in Python 3.6+, the order of categorical values in axes, legends and facets depends on the order in which these values are first encountered in data_frame (and no order is guaranteed by default in Python below 3.6). This parameter is used to force a specific ordering of values per column. The keys of this dict should correspond to column names, and the values should be lists of strings corresponding to the specific display order desired. |
| labels | By default, column names are used in the figure for axis titles, legend entries and hovers. This parameter allows this to be overridden. The keys of this dict should correspond to column names, and the values should correspond to the desired label to be displayed. |
| color_discrete_sequence | Strings should define valid CSS-colors. When color is set and the values in the corresponding column are not numeric, values in that column are assigned colors by cycling through color_discrete_sequence in the order described in category_orders, unless the value of color is a key in color_discrete_map. Various useful color sequences are available in the plotly.express.colors submodules, specifically plotly.express.colors.qualitative. |
| color_discrete_map | String values should define valid CSS-colors Used to override color_discrete_sequence to assign a specific colors to marks corresponding with specific values. Keys in color_discrete_map should be values in the column denoted by color. Alternatively, if the values of color are valid colors, the string ‘identity’ may be passed to cause them to be used directly. |
| orientation | (default ‘v’ if x and y are provided and both continuous or both categorical, otherwise ‘v’`(‘h’) if `x`(`y) is categorical and y`(`x) is continuous, otherwise ‘v’`(‘h’) if only `x`(`y) is provided) |
| boxmode | One of ‘group’ or ‘overlay’ In ‘overlay’ mode, boxes are on drawn top of one another. In ‘group’ mode, baxes are placed beside each other. |
| log_x | If True, the x-axis is log-scaled in cartesian coordinates. |
| log_y | If True, the y-axis is log-scaled in cartesian coordinates. |
| range_x | If provided, overrides auto-scaling on the x-axis in cartesian coordinates. |
| range_y | If provided, overrides auto-scaling on the y-axis in cartesian coordinates. |
| points | One of ‘outliers’, ‘suspectedoutliers’, ‘all’, or False. If ‘outliers’, only the sample points lying outside the whiskers are shown. If ‘suspectedoutliers’, all outlier points are shown and those less than 4*Q1-3*Q3 or greater than 4*Q3-3*Q1 are highlighted with the marker’s ‘outliercolor’. If ‘outliers’, only the sample points lying outside the whiskers are shown. If ‘all’, all sample points are shown. If False, no sample points are shown and the whiskers extend to the full range of the sample. |
| notched | If True, boxes are drawn with notches. |
| title | The figure title. |
| template | The figure template name (must be a key in plotly.io.templates) or definition. |
| width | The figure width in pixels. |
| height | The figure height in pixels. |
Example 1: Using Iris Dataset
Python3
import plotly.express as pxdf = px.data.iris()fig = px.box(df, x="sepal_width", y="sepal_length")fig.show() |
Output:
Example 2: Using Tips Dataset
Python3
import plotly.express as pxdf = px.data.tips()fig = px.box(df, x = "sex", y="total_bill")fig.show() |
Output:
In the above examples, let’s take the first box plot of the figure and understand these statistical things:
- Bottom horizontal line of box plot is minimum value
- First horizontal line of rectangle shape of box plot is First quartile or 25%
- Second horizontal line of rectangle shape of box plot is Second quartile or 50% or median.
- Third horizontal line of rectangle shape of box plot is third quartile or 75%
- Top horizontal line of rectangle shape of box plot is maximum value.
- Small diamond shape of blue box plot is outlier data or erroneous data.
Changing Algorithm for Quartiles
The algorithm to choose quartiles can also be selected in plotly. It is computed by using linear algorithm by default. However, it provides two more algorithms for doing the same i.e. inclusive and exclusive.
Example 1: Using inclusive algorithm
Python3
import plotly.express as pxdf = px.data.tips()fig = px.box(df, x = "sex", y="total_bill", points="all")fig.update_traces(quartilemethod="inclusive")fig.show() |
Output:
Example 2: Using exclusive algorithm
Python3
import plotly.express as pxdf = px.data.tips()fig = px.box(df, x = "sex", y="total_bill", points="all")fig.update_traces(quartilemethod="exclusive")fig.show() |
Output:
Showing the underlying data
Underlying data can be shows using the points arguments. The value of this argument can be of three types –
- all for all points
- outliers for outliers only
- false for none of the above
Example 1: Passing all as argument
Python3
import plotly.express as pxdf = px.data.tips()fig = px.box(df, x = "sex", y="total_bill", points="all")fig.show() |
Output:
Example 2:
Python3
import plotly.express as pxdf = px.data.tips()fig = px.box(df, x = "sex", y="total_bill", points="outliers")fig.show() |
Output:
Styling box plot
Boxplot comes with various styling options. Let’s see one such option in the below example.
Example:
Python3
import plotly.express as pxdf = px.data.tips()fig = px.box(df, x = "sex", y="total_bill", points="all", notched=True)fig.update_traces(quartilemethod="exclusive")fig.show() |
Output:
