Use this function to form a single row from the rows with identical attribute value. For any other attribute (i.e. columns) you need to decide, how to aggregate their attribute values.
Grouping can be specified for one or several columns.
Example: You want to determine the average length of links of type 20. For that purpose, group the links by attribute TypeNo in the list. For the length attribute, select the aggregate function Average.
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Notes: You can use Copy&Paste to output the numbers (Copying and pasting selected attribute values). This function is not available for statistics lists. |
1. Make sure that the list window of the required list is open.
2. Select the columns by which you want to group the data (Selecting list sections).
3. Right-click one of the columns you selected.
The context menu opens.
4. Select the Group columns entry
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Tip: Alternatively, you can define the grouping in the attribute selection window (Editing the display properties of attributes). |
The list appears grouped. The headers of those columns which have been selected for grouping will change to Grp(<column header>). Visum aggregates the other attribute values of the grouped data rows. The particular function that has been selected for the aggregation is displayed in the column header. Subsequently you can select a different aggregate function for each column.
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Notes: In grouped lists, attribute value editing is restricted. The automatic synchronization of a grouped list with the Network editor window is no longer active. We recommend that when grouping data in lists that contain lots of entries, such as PrT paths or path sequences, you only output the columns you wish to analyze, as all the data in the columns displayed is analyzed and re-calculated. |
Selecting an aggregate function for a column in a grouped list
1. Make sure that a list window with a grouped list has been opened.
2. With the right mouse key, click in the header of the selected column.
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Note: In the header of the selected column, the currently used aggregate function is displayed. |
The context menu opens.
3. Select the Aggregate function entry and the desired sub-entry.
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Element |
Description |
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Minimum |
Minimum of the summarized attribute values |
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Maximum |
Maximum of the summarized attribute values |
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Average |
Mean value of the summarized attribute values |
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Weighted mean |
Mean value of the summarized attribute values, weighted by an attribute. If this aggregate function is selected, initially 1.0 is set for weighting. You then select the desired attribute for weighting. To do so, in the Weight column, click the symbol Example: You want to calculate the average volume for a selected link type. Thereby, you would like to prioritize longer links accordingly over shorter ones. For that purpose, aggregate the list by link type, select 'weighted mean' as aggregate function for the volumes, and for the weighting attribute, select 'length'. |
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Sum |
Sum of summarized attribute values |
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Headway |
Group attributes by headway Note This function is only available for attributes of the type time period. If the times correspond to the regular service groups of the procedure Calculate regular services groups, the regular service times are output as strings (Editing regular services). |
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Compare |
If all summarized attribute values are equal, this value is entered, otherwise * appears. |
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Number |
Number of summarized rows |
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Concatenate |
All attribute values of the summarized rows, separated by a separator You can select a different separator (Settings for decimal places, aggregation functions, and connecting journeys). |
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Histogram |
Numbers of occurrence of the summarized attribute values, separated by a separator Format: [value1:number1],[value2:number2], etc. You can select a different separator (Settings for decimal places, aggregation functions, and connecting journeys). |
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Distinct occurrence |
List of the occurring values |
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First value |
Display of the first value of Concatenate |
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Last value |
Display of the last value of Concatenate |
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Empty |
No entry |
According to the selected aggregate function, the values are aggregated.
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Note: If the list includes an attribute multiple times, you can aggregate these attribute values in different ways. |
Ungroup columns
1. Make sure that a list window with a grouped list has been opened.
2. Select the column you would like to ungroup.
3. With the right mouse key, click the header of the selected column.
The context menu opens.
4. Select the desired entry.
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Element |
Description |
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Ungroup selected columns |
The selected columns are no longer grouped. |
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Ungroup all columns |
The list no longer contains grouped columns. |
The grouping is released.
