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Version: Python

How to create histograms

This guide shows you how to use the plot_xy_hist method to create histograms.

The histogram is used to show how frequently different data values occur. The data is divided into logical intervals (or bins) , which are then aggregated and charted with vertical bars. Unlike bar charts (category plots), bars in histograms do not have spaces between them unless there is a gap in the data.

Data sourcing​

From a table​

When data is sourced from a table, the following syntax can be used:

.plot_xy_hist(series_name="series_name", t, x="XCol", nbins).show()

  • plot_xy_hist is the method used to create a histogram.
  • series_name is the name (as a string) you want to use to identify the series on the chart itself.
  • t is the table that holds the data you want to plot.
  • x is the name of the column (as a string) of data to be used for the X values.
  • nbins is the integer number of intervals to use in the chart.
  • show tells Deephaven to draw the plot in the console.
from deephaven.plot.figure import Figure
from deephaven import new_table
from deephaven.column import int_col

source = new_table([int_col("Values", [1, 2, 2, 3, 3, 3, 4, 4, 5])])

new_plot = (
    Figure()
    .plot_xy_hist(series_name="Histogram Values", t=source, x="Values", nbins=5)
    .chart_title(title="Histogram of Values")
    .show()
)

The plot_xy_hist method assumes you want to plot the entire range of values in the dataset. However, you can also set the minimum and maximum values of the range using xmin and xmax respectively:

.plot_xy_hist(series_name, t, x, xmin, xmax, nbins).show()

  • plot_xy_hist is the method used to create a histogram.
  • series_name is the name (as a string) you want to use to identify the series on the chart itself.
  • t is the table that holds the data you want to plot.
  • x is the name of the column (as a string) of data to be used for the X values.
  • xmin is a floating point minimum value in the x column you want to include in the plot.
  • xmax is a floating point maximum value in the x column you want to include in the plot.
  • nbins is the number of intervals to use in the chart.
  • show tells Deephaven to draw the plot in the console.
from deephaven.plot.figure import Figure
from deephaven import new_table
from deephaven.column import int_col

source = new_table([int_col("Values", [1, 2, 2, 3, 3, 3, 4, 4, 5])])

new_plot = (
    Figure()
    .plot_xy_hist(
        series_name="Histogram Values",
        t=source,
        x="Values",
        xmin=2.0,
        xmax=4.0,
        nbins=5,
    )
    .chart_title(title="Histogram of Values")
    .show()
)

From an array​

When data is sourced from an array, the following syntax can be used:

.histPlot(seriesName, x, nbins).show()

  • histPlot is the method used to create a histogram.

  • seriesName is the name (as a string) you want to use to identify the series on the chart itself.

  • x is the array containing the data to be used for the X values.

  • nbins is the number of intervals to use in the chart.

  • show tells Deephaven to draw the plot in the console.

from deephaven.plot.figure import Figure
from numpy import array

source = array([1, 2, 2, 3, 3, 3, 4, 4, 5])

new_plot = (
    Figure()
    .plot_xy_hist(series_name="Histogram Values", x=list(source), nbins=5)
    .chart_title(title="Histogram of Values")
    .show()
)

Just like with a Deephaven table, you can also set the minimum and maximum values of the range using xmin and xmax respectively:

.plot_xy_hist(series_name, x, xmin, xmax, nbins).show()

  • plot_xy_hist is the method used to create a histogram.
  • series_name is the name (as a string) you want to use to identify the series on the chart itself.
  • x is the array containing the data to be used for the X values.
  • xmin is the minimum value (as a double) of the range to be included.
  • xmax is the maximum value (as a double) of the range to be included.
  • nbins is the integer number of the intervals to use in the chart.
  • show tells Deephaven to draw the plot in the console.
from deephaven.plot.figure import Figure
from numpy import array

source = array([1, 2, 2, 3, 3, 3, 4, 4, 5])

new_plot = (
    Figure()
    .plot_xy_hist(
        series_name="Histogram Values", x=list(source), xmin=2.0, xmax=4.0, nbins=5
    )
    .chart_title(title="Histogram of Values")
    .show()
)