ecdf-plots.md

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Overview

Empirical cumulative distribution function plots are a way to visualize the distribution of a variable, and Plotly Express has a built-in function, px.ecdf() to generate such plots. Plotly Express is the easy-to-use, high-level interface to Plotly, which operates on a variety of types of data and produces easy-to-style figures.

Alternatives to ECDF plots for visualizing distributions include histograms, violin plots, box plots and strip charts.

Simple ECDF Plots

Providing a single column to the x variable yields a basic ECDF plot.

importplotly.expressaspxdf=px.data.tips() fig=px.ecdf(df, x="total_bill") fig.show()

Providing multiple columns leverage's Plotly Express' wide-form data support to show multiple variables on the same plot.

importplotly.expressaspxdf=px.data.tips() fig=px.ecdf(df, x=["total_bill", "tip"]) fig.show()

It is also possible to map another variable to the color dimension of a plot.

importplotly.expressaspxdf=px.data.tips() fig=px.ecdf(df, x="total_bill", color="sex") fig.show()

Configuring the Y axis

By default, the Y axis shows probability, but it is also possible to show raw counts by setting the ecdfnorm argument to None or to show percentages by setting it to percent.

importplotly.expressaspxdf=px.data.tips() fig=px.ecdf(df, x="total_bill", color="sex", ecdfnorm=None) fig.show()

If a y value is provided, the Y axis is set to the sum of y rather than counts.

importplotly.expressaspxdf=px.data.tips() fig=px.ecdf(df, x="total_bill", y="tip", color="sex", ecdfnorm=None) fig.show()

Reversed and Complementary CDF plots

By default, the Y value represents the fraction of the data that is at or below the value on on the X axis. Setting ecdfmode to "reversed" reverses this, with the Y axis representing the fraction of the data at or above the X value. Setting ecdfmode to "complementary" plots 1-ECDF, meaning that the Y values represent the fraction of the data above the X value.

In standard mode (the default), the right-most point is at 1 (or the total count/sum, depending on ecdfnorm) and the right-most point is above 0.

importplotly.expressaspxfig=px.ecdf(df, x=[1,2,3,4], markers=True, ecdfmode="standard", title="ecdfmode='standard' (Y=fraction at or below X value, this the default)") fig.show()

In reversed mode, the right-most point is at 1 (or the total count/sum, depending on ecdfnorm) and the left-most point is above 0.

importplotly.expressaspxfig=px.ecdf(df, x=[1,2,3,4], markers=True, ecdfmode="reversed", title="ecdfmode='reversed' (Y=fraction at or above X value)") fig.show()

In complementary mode, the right-most point is at 0 and no points are at 1 (or the total count/sum) per the definition of the CCDF as 1-ECDF, which has no point at 0.

importplotly.expressaspxfig=px.ecdf(df, x=[1,2,3,4], markers=True, ecdfmode="complementary", title="ecdfmode='complementary' (Y=fraction above X value)") fig.show()

Orientation

By default, plots are oriented vertically (i.e. the variable is on the X axis and counted/summed upwards), but this can be overridden with the orientation argument.

importplotly.expressaspxdf=px.data.tips() fig=px.ecdf(df, x="total_bill", y="tip", color="sex", ecdfnorm=None, orientation="h") fig.show()

Markers and/or Lines

ECDF Plots can be configured to show lines and/or markers.

importplotly.expressaspxdf=px.data.tips() fig=px.ecdf(df, x="total_bill", color="sex", markers=True) fig.show()

importplotly.expressaspxdf=px.data.tips() fig=px.ecdf(df, x="total_bill", color="sex", markers=True, lines=False) fig.show()

Marginal Plots

ECDF plots also support marginal plots

importplotly.expressaspxdf=px.data.tips() fig=px.ecdf(df, x="total_bill", color="sex", markers=True, lines=False, marginal="histogram") fig.show()

importplotly.expressaspxdf=px.data.tips() fig=px.ecdf(df, x="total_bill", color="sex", marginal="rug") fig.show()

Facets

ECDF Plots also support faceting

importplotly.expressaspxdf=px.data.tips() fig=px.ecdf(df, x="total_bill", color="sex", facet_row="time", facet_col="day") fig.show()