Line Chart¶
This section showcases the line chart. It contains examples of how to create line charts using the datachart.charts.LineChart function.
The examples sequentially build on each other, going from simple to more complex.
As mentioned above, the line charts are created using the LineChart function found in the datachart.charts module. Let's import it:
from datachart.charts import LineChart
Double figure generation avoidence
To avoid double figure generation, the LineChart function is preceded by the _ = operator. The double figures are generated because LineChart returns the plt.Figure object, which is then used to save the figure locally.
Line Chart Input Attributes¶
The LineChart function accepts keyword arguments for chart configuration. The main argument is data, which contains the data points. For a single line chart, data is a list of dictionaries. For multiple line charts, data is a list of lists.
LineChart(
data=[{ # A list of line data points (or list of lists for multiple charts)
"x": Union[int, float], # The x-axis value
"y": Union[int, float], # The y-axis value
"yerr": Optional[Union[int, float]] # The y-axis error value (to plot the confidence interval)
}],
style={ # The style of the line (optional)
"plot_line_color": Optional[str], # The color of the line (hex color code)
"plot_line_style": Optional[LINE_STYLE], # The line style (solid, dashed, etc.)
"plot_line_marker": Optional[LINE_MARKER], # The marker style of the line (circle, square, etc.)
"plot_line_width": Optional[float], # The width of the line
"plot_line_alpha": Optional[float], # The alpha of the line (how visible the line is)
"plot_line_drawstyle": Optional[LINE_DRAW_STYLE], # The drawstyle of the line (step, steps-mid, etc.)
"plot_line_zorder": Optional[int], # The zorder of the line
},
subtitle=Optional[str], # The subtitle of the chart (or list for multiple charts)
title=Optional[str], # The title of the chart
xlabel=Optional[str], # The x-axis label
ylabel=Optional[str], # The y-axis label
xticks=Optional[List[Union[int, float]]], # the x-axis ticks
xticklabels=Optional[List[str]], # the x-axis tick labels (must be same length as xticks)
xtickrotate=Optional[int], # the x-axis tick labels rotation
yticks=Optional[List[Union[int, float]]], # the y-axis ticks
yticklabels=Optional[List[str]], # the y-axis tick labels (must be same length as yticks)
ytickrotate=Optional[int], # the y-axis tick labels rotation
vlines=Optional[Union[dict, List[dict]]], # the vertical lines (see below for more details)
hlines=Optional[Union[dict, List[dict]]], # the horizontal lines (see below for more details)
)
For more details, see the datachart.typings.LineChartAttrs type.
Single Line Chart¶
In this part, we show how to create a single line chart using the LineChart function.
Let us first import the necessary libraries:
import numpy as np
Basic example. Let us first create a basic line chart showing the cosine function.
The following example shows how only the data argument is required to draw the line chart.
_ = LineChart(
# add the data to the chart
data=[{"x": x / 10, "y": np.cos(x / 2)} for x in range(21)]
)
Chart title and axis labels¶
To add the chart title and axis labels, simply add the title, xlabel and ylabel attributes.
_ = LineChart(
data=[{"x": x / 10, "y": np.cos(x / 2)} for x in range(21)],
# add the title
title="Title",
# add the x and y axis labels
xlabel="the global x-axis label",
ylabel="the global y-axis label"
)
Figure size and grid¶
To change the figure size, simply add the figsize attribute. The figsize attribute can be a tuple (width, height), values are in inches. The datachart package provides a datachart.constants.FIG_SIZE constant, which contains some of the predefined figure sizes.
To add the grid, simply add the show_grid attribute. The possible options are:
| Option | Description |
|---|---|
"both" |
shows both the x-axis and the y-axis gridlines. |
"x" |
shows only the x-axis grid lines. |
"y" |
shows only the y-axis grid lines. |
Again, datachart provides a datachart.constants.SHOW_GRID constant, which contains the supported options.
from datachart.constants import FIG_SIZE, SHOW_GRID
_ = LineChart(
data=[{"x": x / 10, "y": np.cos(x / 2)} for x in range(21)],
title="Title",
xlabel="the global x-axis label",
ylabel="the global y-axis label",
# add to determine the figure size
figsize=FIG_SIZE.A4_NARROW,
# add to show the grid lines
show_grid=SHOW_GRID.BOTH
)
Line style¶
To change a single line style simply add the style attribute with the corresponding attributes. The supported attributes are shown in the datachart.typings.LineStyleAttrs type, which contains the following attributes:
| Attribute | Description |
|---|---|
"plot_line_color" |
The color of the line (hex color code). |
"plot_line_alpha" |
The alpha of the line (how visible the line is). |
"plot_line_width" |
The width of the line. |
"plot_line_style" |
The line style (solid, dashed, etc.). |
"plot_line_marker" |
The marker style of the line (circle, square, etc.). |
"plot_line_drawstyle" |
The drawstyle of the line (step, steps-mid, etc.). |
"plot_line_zorder" |
The zorder of the line. |
Again, to help with the style settings, the datachart.constants module contains the following constants:
| Constant | Description |
|---|---|
| datachart.constants.LINE_STYLE | The line style (solid, dashed, etc.) |
| datachart.constants.LINE_MARKER | The marker style of the line (circle, square, etc.) |
| datachart.constants.LINE_DRAW_STYLE | The drawstyle of the line (step, steps-mid, etc.) |
from datachart.constants import LINE_STYLE, LINE_MARKER, LINE_DRAW_STYLE
_ = LineChart(
data=[{"x": x / 10, "y": np.cos(x / 2)} for x in range(21)],
# define the style of the line
style={
"plot_line_style": LINE_STYLE.DOTTED,
"plot_line_marker": LINE_MARKER.POINT,
"plot_line_drawstyle": LINE_DRAW_STYLE.STEPS_MID,
},
title="Title",
xlabel="the global x-axis label",
ylabel="the global y-axis label",
figsize=FIG_SIZE.A4_NARROW,
show_grid=SHOW_GRID.BOTH
)
Area under the line¶
To add the area under the line, simply add the show_area argument.
_ = LineChart(
data=[{"x": x / 10, "y": np.cos(x / 2)} for x in range(21)],
style={
"plot_line_style": LINE_STYLE.DOTTED,
"plot_line_marker": LINE_MARKER.POINT,
"plot_line_drawstyle": LINE_DRAW_STYLE.STEPS_MID,
},
title="Title",
xlabel="the global x-axis label",
ylabel="the global y-axis label",
figsize=FIG_SIZE.A4_NARROW,
show_grid=SHOW_GRID.BOTH,
# shows the area between the line and y=0
show_area=True
)
Adding vertical and horizontal lines¶
Adding vertical lines. Use the vlines argument with the datachart.typings.VLinePlotAttrs typing, which is either a dict or a List[dict] where each dictionary contains some of the following attributes:
{
"x": Union[int, float], # The x-axis value
"ymin": Optional[Union[int, float]], # The minimum y-axis value
"ymax": Optional[Union[int, float]], # The maximum y-axis value
"style": { # The style of the line (optional)
"plot_vline_color": Optional[str], # The color of the line (hex color code)
"plot_vline_style": Optional[LINE_STYLE], # The line style (solid, dashed, etc.)
"plot_vline_width": Optional[float], # The width of the line
"plot_vline_alpha": Optional[float], # The alpha of the line (how visible the line is)
},
"label": Optional[str], # The label of the line
}
Adding horizontal lines. Use the hlines argument with the datachart.typings.HLinePlotAttrs typing, which is either a dict or a List[dict] where each dictionary contains some of the following attributes:
{
"y": Union[int, float], # The y-axis value
"xmin": Optional[Union[int, float]], # The minimum x-axis value
"xmax": Optional[Union[int, float]], # The maximum x-axis value
"style": { # The style of the line (optional)
"plot_hline_color": Optional[str], # The color of the line (hex color code)
"plot_hline_style": Optional[LINE_STYLE], # The line style (solid, dashed, etc.)
"plot_hline_width": Optional[float], # The width of the line
"plot_hline_alpha": Optional[float], # The alpha of the line (how visible the line is)
},
"label": Optional[str], # The label of the line
}
To add vertical and horizontal lines, simply add the vlines and hlines arguments.
_ = LineChart(
data=[{"x": x / 10, "y": np.cos(x / 2)} for x in range(21)],
style={
"plot_line_style": LINE_STYLE.DOTTED,
"plot_line_marker": LINE_MARKER.POINT,
"plot_line_drawstyle": LINE_DRAW_STYLE.STEPS_MID,
},
# add a list of vertical lines
vlines=[
{
"x": 0.5 * i,
"style": {
"plot_vline_color": "green",
"plot_vline_style": LINE_STYLE.SOLID,
"plot_vline_width": 1,
},
}
for i in range(1, 4)
],
# add a list of horizontal lines
hlines={
"y": 0,
"style": {
"plot_hline_color": "red",
"plot_hline_style": LINE_STYLE.DASHED,
"plot_hline_width": 2,
"plot_hline_alpha": 0.5,
},
},
title="Title",
xlabel="the global x-axis label",
ylabel="the global y-axis label",
figsize=FIG_SIZE.A4_NARROW,
show_grid=SHOW_GRID.BOTH,
)
Multiple Line Charts¶
To create multiple line charts, pass a list of lists to the data argument. Each inner list represents the data for one line. Per-chart attributes like subtitle and style can be passed as lists, where each element corresponds to a chart.
Multiple charts pattern
For multiple charts, data becomes a list of lists, and per-chart attributes like subtitle and style become lists where each element applies to the corresponding chart.
_ = LineChart(
# use a list of lists to define multiple lines
data=[
[{"x": x / 10, "y": np.cos(x / 2)} for x in range(21)],
[{"x": x / 10, "y": 2 * np.sin(x / 2)} for x in range(21)],
],
# style can be a list (one per chart) or a single dict (applies to all)
style=[
{
"plot_line_style": LINE_STYLE.DOTTED,
"plot_line_marker": LINE_MARKER.POINT,
"plot_line_drawstyle": LINE_DRAW_STYLE.STEPS_MID,
},
None, # use default style for the second line. Also supports: {}
],
title="Title",
xlabel="the global x-axis label",
ylabel="the global y-axis label",
figsize=FIG_SIZE.A4_NARROW,
show_grid=SHOW_GRID.BOTH,
)
Sub-chart subtitles¶
We can name each chart by passing a list of subtitles to the subtitle argument. In addition, to help with discerning which chart is which, use the show_legend argument to show the legend of the charts.
_ = LineChart(
data=[
[{"x": x / 10, "y": np.cos(x / 2)} for x in range(21)],
[{"x": x / 10, "y": 2 * np.sin(x / 2)} for x in range(21)],
],
style=[
{
"plot_line_style": LINE_STYLE.DOTTED,
"plot_line_marker": LINE_MARKER.POINT,
"plot_line_drawstyle": LINE_DRAW_STYLE.STEPS_MID,
},
None,
],
# add a subtitle to each line
subtitle=["cosine", "sine"],
title="Title",
xlabel="the global x-axis label",
ylabel="the global y-axis label",
figsize=FIG_SIZE.A4_NARROW,
show_grid=SHOW_GRID.BOTH,
# show the legend
show_legend=True,
)
Subplots¶
To draw multiple charts in each subplot, simply add the subplots attribute. The chart's subtitle are then added at the top of each subplot, while the title, xlabel and ylabel are positioned to be global for all charts.
_ = LineChart(
data=[
[{"x": x / 10, "y": np.cos(x / 2)} for x in range(21)],
[{"x": x / 10, "y": 2 * np.sin(x / 2)} for x in range(21)],
],
style=[
{
"plot_line_style": LINE_STYLE.DOTTED,
"plot_line_marker": LINE_MARKER.POINT,
"plot_line_drawstyle": LINE_DRAW_STYLE.STEPS_MID,
},
None,
],
subtitle=["cosine", "sine"],
title="Title",
xlabel="the global x-axis label",
ylabel="the global y-axis label",
figsize=FIG_SIZE.A4_NARROW,
show_grid=SHOW_GRID.BOTH,
# show each chart in its own subplot
subplots=True,
)
Sharing x-axis and/or y-axis across subplots¶
To share the x-axis and/or y-axis across subplots, simply add the sharex and/or sharey attributes, which are boolean values that specify whether to share the axis across all subplots.
_ = LineChart(
data=[
[{"x": x / 10, "y": np.cos(x / 2)} for x in range(21)],
[{"x": x / 10, "y": 2 * np.sin(x / 2)} for x in range(21)],
],
style=[
{
"plot_line_style": LINE_STYLE.DOTTED,
"plot_line_marker": LINE_MARKER.POINT,
"plot_line_drawstyle": LINE_DRAW_STYLE.STEPS_MID,
},
None,
],
subtitle=["cosine", "sine"],
title="Title",
xlabel="the global x-axis label",
ylabel="the global y-axis label",
figsize=FIG_SIZE.A4_NARROW,
show_grid=SHOW_GRID.BOTH,
subplots=True,
# share the x-axis across all subplots
sharex=True,
# share the y-axis across all subplots
sharey=True,
)
Area under the lines¶
Specifying the show_area attribute will show the area between the line and y=0 across all subplots.
_ = LineChart(
data=[
[{"x": x / 10, "y": np.cos(x / 2)} for x in range(21)],
[{"x": x / 10, "y": 2 * np.sin(x / 2)} for x in range(21)],
],
style=[
{
"plot_line_style": LINE_STYLE.DOTTED,
"plot_line_marker": LINE_MARKER.POINT,
"plot_line_drawstyle": LINE_DRAW_STYLE.STEPS_MID,
},
None,
],
subtitle=["cosine", "sine"],
title="Title",
xlabel="the global x-axis label",
ylabel="the global y-axis label",
figsize=FIG_SIZE.A4_NARROW,
show_grid=SHOW_GRID.BOTH,
subplots=True,
sharex=True,
sharey=True,
# show area between the line and y=0 for all subplots
show_area=True,
)
Confidence interval¶
If a line chart has a confidence interval, it can be added by adding the yerr attribute to the chart's data attribute. Afterwards, the show_yerr attribute can be set to True to show the confidence interval.
import random
_ = LineChart(
data=[
# add the error values for each point's y value
[{"x": x / 10, "y": np.cos(x / 2), "yerr": 0.1 + random.random()} for x in range(21)],
# note: not all lines require to have the error values
[{"x": x / 10, "y": 2 * np.sin(x / 2)} for x in range(21)],
],
style=[
{
"plot_line_style": LINE_STYLE.DOTTED,
"plot_line_marker": LINE_MARKER.POINT,
"plot_line_drawstyle": LINE_DRAW_STYLE.STEPS_MID,
},
None,
],
subtitle=["Subtitle", "Subtitle"],
title="Title",
figsize=FIG_SIZE.A4_NARROW,
show_grid=SHOW_GRID.BOTH,
subplots=True,
sharex=True,
sharey=True,
# show the confidence interval using the error values
show_yerr=True,
)
Additional Features¶
Axis scales¶
The user can change the axis scale using the scalex and scaley attributes. The supported scale options are:
| Options | Description |
|---|---|
"linear" |
The linear scale. |
"log" |
The log scale. |
"symlog" |
The symmetric log scale. |
"asinh" |
The asinh scale. |
Again, to help with the options settings, the datachart.constants module contains the following constants:
| Constant | Description |
|---|---|
| datachart.constants.SCALE | The axis options. |
from datachart.constants import SCALE
To showcase the supported scales, we iterate through all of the scales options.
chart_data = [{"x": x / 10, "y": 1 + np.cos(x / 2)} for x in range(1, 21)]
for scale in [SCALE.LINEAR, SCALE.LOG, SCALE.SYMLOG, SCALE.ASINH]:
figure = LineChart(
data=chart_data,
title=f"Graph showcasing the '{scale}' scale",
xlabel="the global x-axis label",
ylabel="the global y-axis label",
figsize=FIG_SIZE.A4_NARROW,
show_grid=SHOW_GRID.BOTH,
# set the scale of the x and y axes
scalex=scale,
scaley=scale,
)
Saving the Chart as an Image¶
To save the chart as an image, use the datachart.utils.save_figure function.
from datachart.utils import save_figure
save_figure(figure, "./fig_line_chart.png", dpi=300)
The figure should be saved in the current working directory.
Example Use Cases¶
Example 1: ROC curve¶
The example below shows how to create a ROC curve.
data attribute naming convention
By default, the data items should be dictionaries with the following keys: x, y, yerr. However, they can be any other keys. In the example below, the data contains the attributes tp and fp. To let the function know which values are which, you can specify the x and y arguments. This way, the function will know which value to use for the x- and y-axis.
from datachart.constants import HATCH_STYLE
_ = LineChart(
data=[
# note that the attributes are "tp" and "fp", instead of "x" and "y"
[
{"tp": 0, "fp": 0},
{"tp": 0.1, "fp": 0},
{"tp": 0.1, "fp": 0.1},
{"tp": 0.3, "fp": 0.1},
{"tp": 0.3, "fp": 0.2},
{"tp": 0.5, "fp": 0.2},
{"tp": 0.5, "fp": 0.3},
{"tp": 0.8, "fp": 0.3},
{"tp": 0.8, "fp": 0.5},
{"tp": 1.0, "fp": 0.5},
{"tp": 1.0, "fp": 1.0},
],
[
{"tp": 0, "fp": 0},
{"tp": 0.2, "fp": 0},
{"tp": 0.2, "fp": 0.05},
{"tp": 0.8, "fp": 0.05},
{"tp": 0.8, "fp": 0.1},
{"tp": 1.0, "fp": 0.1},
{"tp": 1.0, "fp": 1.0},
],
],
subtitle=["Method 1", "Method 2"],
# specify which attr to use for x and y
x="fp",
y="tp",
style=[
{"plot_area_hatch": HATCH_STYLE.DIAGONAL},
{"plot_area_hatch": HATCH_STYLE.DIAGONAL},
],
title="AUC",
xlabel="False Positive Rate",
ylabel="True Positive Rate",
figsize=(5, 2.8),
show_grid=SHOW_GRID.BOTH,
xmin=0, # the minimum value of the x-axis
xmax=1, # the maximum value of the x-axis
ymin=0, # the minimum value of the y-axis
ymax=1, # the maximum value of the y-axis
show_area=True,
subplots=True,
sharex=True,
sharey=True,
# assign the aspect ratio of all subplots
aspect_ratio="equal",
)
Example 2: Training loss¶
The following example shows how to create a training loss chart.
data attribute naming convention
By default, the data items should be dictionaries with the following keys: x, y, yerr. However, they can be any other keys. In the example below, the data contains the attributes step and loss. To let the function know which values are which, you can specify the x and y arguments. This way, the function will know which value to use for the x- and y-axis.
Let us first update the global config:
from datachart.constants import COLORS
from datachart.config import config
config.update_config(config={"color_general_multiple": COLORS.Dark2})
_ = LineChart(
data=[
# note that the attributes are "step" and "loss", instead of "x" and "y"
[{"step": step, "loss": (0.5 + random.random()) ** step} for step in range(100)],
[{"step": step, "loss": (0.3 + random.random()) ** step} for step in range(100)],
[{"step": step, "loss": (0.2 + random.random()) ** step} for step in range(100)],
],
# specify which attr to use for x and y
x="step",
y="loss",
subtitle=["Method 1", "Method 2", "Method 3"],
title="Training Performance",
xlabel="training steps",
ylabel="training loss",
figsize=FIG_SIZE.A4_NARROW,
show_grid=SHOW_GRID.Y,
show_legend=True,
# depict the y-axis as a log scale
scaley="log",
subplots=False,
)