Histogram

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

Histograms can be plotted using data from tables or arrays.

Creating a Histogram Plot using Data from a Table

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

.histPlot("seriesName", source, "ValueCol", 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.
  • source is the table that holds the data you want to plot.
  • "ValueCol" is the name of the column (as a string) of 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.
tHist = db.t("LearnDeephaven", "StockTrades")
    .where("Date=`2017-08-25`")
    .view("Sym", "Last", "Size", "ExchangeTimestamp")

plotPriceIntervals = histPlot("AAPL", tHist.where("Sym=`AAPL`"), "Last", 10)
    .chartTitle("Price Intervals")
    .show()

from deephaven import Plot

tHist = db.t("LearnDeephaven", "StockTrades")\
    .where("Date=`2017-08-25`")\
    .view("Sym", "Last", "Size", "ExchangeTimestamp")

plotPriceIntervals = Plot.histPlot("AAPL", tHist.where("Sym=`AAPL`"), "Last", 10)\
    .chartTitle("Price Intervals")\
    .show()

This query plots the histogram as follows:

  • plotPriceIntervals is the name of the variable that will hold the chart.
  • histPlot is the method.
  • "AAPL" is the name of the series to use in the chart.
  • trades.where("Sym=`AAPL`") is the source data filtered to AAPL.
  • Last is table column that contains the values we want to plot, and
  • 10 is the number of intervals we want to use to divide up the sales.

img

The histPlot 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 rangeMin and rangeMax respectively:

.histPlot("seriesName", source, "ValueCol", rangeMin, rangeMax, 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.
  • source is the table that holds the data you want to plot.
  • "ValueCol" is the name of the column (as a string) of data to be used for the X values.
  • rangeMin is the minimum value (as a double) of the range to be included.
  • rangeMax is the maximum value (as a double) of the range to be included.
  • nbins is the number of intervals to use in the chart.
  • show tells Deephaven to draw the plot in the console.

Creating a Histogram Plot using Data 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.

The histPlot 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 rangeMin and rangeMax respectively:

.histPlot("SeriesName", [x], rangeMin, rangeMax, 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.
  • rangeMin is the minimum value (as a double) of the range to be included.
  • rangeMax is the maximum value (as a double) of the range to be included.
  • nbins is the number of the intervals to use in the chart.
  • show tells Deephaven to draw the plot in the console.

Additional Options