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App version: 3.4.13

Smoothing in charts

Neptune may transform the data displayed on charts by applying the following:

A chart with and without the manual smoothing applied.

Rendering algorithm ("downsampling")​

Neptune renders charts based on all data points. If there are too many original points to display at once, Neptune renders aggregated values.

info

Neptune can always retrieve 100% accurate values. You can increase the precision of displayed values by zooming in.

To ensure uniform distribution of all data points, the rendering algorithm divides the X axis of a chart into ranges of the same length, then selects a data point to display for each range.

  • If a series has multiple values logged in a given range, the average of the y values is displayed. In addition, the shaded area on the chart represents the minimum and maximum values for that range.
  • If a series doesn't have values logged in a given range, the displayed data point is interpolated based on the values of the surrounding points.

If the X axis displays time instead of steps, the rendered time values are used to calculate the average.

Smoothing function​

When you move the smoothing slider, Neptune applies a simple moving average (SMA) calculation on the y-values that are displayed on the chart. Increasing the smoothing increases the size of the window that's used to determine each point's y-value.

Near the edges of the chart, the input window shrinks to include fewer points. For example, if using the default causal smoothing, at the very left edge the window consists of only the point itself.

note

To make graphs easier to see, the min/max shadow isn't shown when manual smoothing is applied.

Choosing the algorithm​

To select the algorithm to use for all charts in the view, access the global controls:

  • Causal SMA (default): The input window is backward-looking. The average is calculated only from past and present inputs.
  • Centered SMA: The input window is centered. The average is calculated from an equal number of values on each side.

Using the slider​

You can control the smoothing degree with the slider in the local or global chart settings.

The slider position determines the size of the input window as follows:

  • With maximum smoothing, the window comprises 50% of the total rendered points.

    Because data points are typically distributed uniformly over the X axis, this approximately corresponds to 50% of the chart width.

    Chart with the smoothing slider set to 100%.

  • With the smoothing slider in some middle position, the window size is scaled down linearly. For example: With the slider halfway, the window size is 25% of the total points.

    Chart with the smoothing slider set to 50%.

Note that the example images correspond to the Centered SMA algorithm option.

Current limitations
  • In case data points aren't distributed uniformly over the X axis, the average value, as calculated by the SMA smoothing algorithm, may differ from actual average value of the continuous function over the given range.
  • When a chart is zoomed in, only points in the visible range are retrieved and taken into account when smoothing is performed. This can lead to reduced smoothing precision at the edges of the visible range.