Building Chart Dataset
Charts provide several generic ways of fetching tabular data from Iotellect Server context tree and using this data to build chart's dataset.
This section covers chart properties that are related to fetching source data and building chart's dataset.
Data-related Chart Properties
Data Source Type
This basic parameter defines what kind of data should be used to build a chart. There can be four options:
Custom Data. Use custom tabular data to build a chart.
Event. Use data from event history and new event occurrences to build and dynamically update the chart.
Variable. Use data from variable changes history and real-time variable changes to build and dynamically update the chart.
Trending. Use other chart's dataset to build a trend, such as moving average, liner/power regression, etc.
Dependent. Use other chart's dataset to build a dependent chart, which can process source dataset with help of dependent chart bindings.
Custom Data is used in all charts. Event and Variable data types are available in XY Line Chart, XY Area Chart and XY Bar Chart. And Trending is available for the same three charts if they are a part of Mixed XY Chart.
Property name: source
Property type: Integer
Source Events
This property defines what is used to build an event-based chart. It has a tabular format. Every line in the table defines one data series to be shown on the chart. Thus, a single chart may show changes of different values, and even values calculated from the data of different events.
Each data series has the following properties:
Property | Type | Description | |
Name | String | Name of data series indicated on the chart. | |
Context | String | Server context defining event to take the data from. | |
Event | String | Event from which to take the data. | |
Expression | String | Expression used to calculate data values. In most cases it should include references to the cells of event Data Table. | |
Variable Series Expression Resolution Environment: | |||
|---|---|---|---|
Specified by series Context setting. | |||
Value of variable specified by series Event setting. | |||
0 | |||
Standard variables only. | |||
Date Expression | String | Expression used to calculate value timestamps (i.e. domain axis values). If this expression is not defined (this is a default behaviour), chart represents values at timestamps when their modification was registered by the server. The Date Expression is useful when variable value Data Tables received from a device (e.g. a real-time controller) contains both timestamps and values. In this case each data sample contains both domain-axis value (the timestamp) and range-axis value (the number), precisely positioning a chart data item. | |
Variable Series Date Expression Resolution Environment: | |||
Specified by series Context setting. | |||
Value of variable specified by series Event setting. | |||
0 | |||
Standard variables only. | |||
Aggregation | Integer | Tells what to do if several data values exist for a specific time range. Possible choices are calculate an average, take minimal or maximal value, calculate a sum of all values, or take first/last value for the period. | |
Property name: eventSeries
Property type: Data Table
Source Variables
This property defines what data is used to build a variable-based chart. It is formatted as a table. Every line in the table defines one data series to be shown on the chart. Thus, a single chart may show changes of different values, and even values calculated from data of different variables.
Each data series has the following properties:
Property | Type | Description | |
Name | String | Name of data series indicated on the chart. Series name can be an expression or just a string constant. | |
Context | String | Server context defining event to take the data from. | |
Variable | String | Variable from which to take the data. | |
Expression | String | Expression used to calculate data values. In most cases it should include references to the variable value. | |
Variable Series Expression Resolution Environment: | |||
|---|---|---|---|
Specified by series Context setting. | |||
Value of variable specified by series Variable setting. | |||
0 (or dynamic if series propagation is enabled) | |||
Standard variables only. | |||
Propagate | Boolean | Create a separate data series for every record of source variable. See series propagation for details. | |
Aggregation | Integer | Tells what to do if several data values exist for a specific time range. Possible choices are calculate an average, take minimal or maximal value, calculate a sum of all values, or take first/last value for the period. | |
Type | Integer | Data series type. | |
Property name: variableSeries
Property type: Data Table
Time Unit
Time unit defines resolution for event-based and variable-based charts. Only one data value per time unit is shown on the chart. For example, if time unit for Event chart is Day and several events occurred during a certain day, data for only one event for this day (the latest one) is shown on the chart.
Available Time Units: Year, Quarter, Month, Week, Day, Hour, Minute and Second.
Property name: timeUnit
Property type: Integer
Include Historical Data
This property specifies whether an event-based or variable-based chart will include historical data, i.e. events and variable value changes that occurred before the chart was built.
 | Estimate memory consumption that may be caused by loading historical data according to Limit Time Range and Time Range options. Loading a huge amount of historical data may cause server failure or degraded performance. |
Property name: includeHistory
Property type: Boolean
Include Real-Time Data
This property specifies whether event-based and variable-based charts include real-time data, i.e. data for changes that occur after the chart is built. If this option is enabled, the chart is updated every time a new event is registered or a variable's value is changed.
Property name: includeRealtime
Property type: Boolean
Limit Time Range
This property is relevant for event-based and variable-based charts. Supported values are:
Full History. All historical values will be loaded and displayed.
Last Values. Chart data will include only events and variable value changes that have occurred only within a certain time before the chart is built, as specified by the Time Range property.
Date Range. Chart data will only include values that were obtained within a time range specified by Start Date and End Date properties.
| Disabling limited time range will force the server to load all available event/variable history from database into memory in order to prepare chart dataset. This may cause very high memory consumption and lead to server failure of degraded performance! |
Property name: enableTimeRange
Property type: Boolean
Time Range (in Time Units)
This option is available only if Limit Time Range setting is enabled. It specifies a number of Time Units defining time range for a chart.
| Setting a long time range will force the server to load a sufficient part of event/variable history from database into memory in order to prepare chart dataset. This may cause very high memory consumption and lead to server failure of degraded performance! |
Property name: timeRange
Property type: Integer
Start Date
Low bound timestamp of displayed historical values range. Available if Limit Time Range is set to Date Range.
Property name: startDate
Property type: Date
End Date
High bound timestamp of displayed historical values range. Available if Limit Time Range is set to Date Range.
Property name: endDate
Property type: Date
Source Data
The source data table used for building custom-data-based charts.
Property name: sourceData
Property type: Data Table
Source Data Bindings
A set of expressions used to retrieve data from Source Data table records and build the resulting chart dataset. This property is also valid only for charts based on custom data.
Property name: chartBindings
Property type: Data Table
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