Time Series Modifiers

This display is used to apply changes to time series within the FEWS database. the definition of modification to a time series is that a change is made to that time series without actually editing the values themselves. The changes are established as a "description of the change". This could be for example the increase of an observed level by 2 cm over a given time period. It could also be applied as an edited time series to replace the original time series. On retrieval of a time series from the database, the data access layer checks if there are any modifiers applicable to the data being extracted. If relevant modifiers are found, then these are applied before the data is passed to the module that has requested the data. The module itself is not "aware" that the data has been amended by a modifiers. The diagram below illustrates this process.

Modifiers can be entered and managed through the Time Series Modifier Display.

Time Series Modifier Display

Modifiers are defined through the modifier display, which can be opened either through the FEWS explorer menu, or through the toolbar on the main window (when configured).

The modifier display contains five sections;
• A tree view of the pre-configured display groups containing links to time series to which modifiers can be applied.
• A panel allowing the user to select the specific location to which a modifier is to be applied.
• A panel allowing the user to select the specific parameter to which a modifier is to be applied.
• A main window showing time series contained in the display group selected.
• An information panel allowing new modifiers to be defined, and existing modifiers to be managed.

Selecting a time series to which a modifier is to be applied

To select the time series to which the modifier is to be applied, identify and select the display group in which the time series is contained in the tree view on the left.

Once a display has been selected, the locations panel will show all locations available in the display group selected. Select the desired location.

Once a parameter has been selected, the parameters panel will show all parameters available at the locations selected. Select the desired parameter.

Following selection of the parameters the selection will be visible in the Create New tab of the Modifier information panel.

Creating a new modifier

To create a new modifier, select the time series (location & parameter) to which the modifier is to be defined.

Open the Create New tab in the Modifier information panel.

Select the name of the modifier. On selection the name defaults to a combination of the location Id and the parameter Id.

Enter an appropriate description for the modifier. This is optional and can be displayed later when managing existing modifiers.

Define the start time and the end time of the data to change. By default the times defined are equal to the time series displayed in the main window.

Define the start time and the end time of the validity period of the modifier. By default the times defined are equal to the time series displayed in the main window.

Select the modifier operation and enter the value with which the data is to be changed. A value does not need to be added if the option to Edit the data or to replace it with a missing value is selected. If the option to Edit the data has been selected, use the interactive edit facility to define the changes.

Select Create on completion of the modifier.

Modifier Operations

The types of modifier that are available are:
• Add - allows a value to be added to the original data for a defined time span.
• Subtract- allows a value to be subtracted from the original data for a defined time span
• Multiply - allows a value to be given with which original data is multiplied for a defined time span.
• Divide - allows a value to be given with which original data is divided for a defined time span.
• Replace - allows a value to be given that replaces the original data for a defined time span.
• Missing - allows the original values with missing data for a defined time span.
• Time Shift - allows a time increment to be defined with which the original data is to be shifted (not yet available).
• Edit - allows a time series of values to be defined either as a table of values or through interactive editing on the graph, which replace the time series for a defined time span.

Modifier change start and end time

A modifier is applied to the original data for a defined time span. This is defined as a start time and an end time. These times relate to the data in the time series, and not to the time on the computer.

The start and end time can be changed by entering the date and time values in the appropriate input boxes. These can also be changed by clicking on the display. Through the right mouse button a menu is available that allows selection of either the start time or the end time.

Start and end times selected are displayed as vertical lines in the display.