# Merge ratio matrix

Merge ratio matrix is used to view topic merges between topic map layers in Wandora. Wandora can contain several separate topic maps at a time. These topic maps are called as topic map layers. It is very common that some topics locate in more than one layer i.e. several layers include the topic. Merge ratio matrix is a matrix where each row and column represent one topic map layer in Wandora. If user has three topic map layers in Wandora, the merge ratio matrix contains three rows and three columns. Each matrix cell number is the ratio of merged topics and all topics in these layers. Thus, diagonal cell values are always 1 as row topic map is same as the column topic map, and topic maps merge completely.

Merge ratio matrix tool starts with a menu option **Layers > Statistics > Merge ratio matrix...**.

## Example

Wandora samples contains a project ArtofNoise.wpr which consists of three layers. Wandora user opens the project and selects menu option **Layers > Statistics > Merge ratio matrix...**. User chooses to **not** to count percentages.

After clicking the OK button, Wandora calculates and views the merge matrix.

User should note that diagonal values are 1/1 as row and column topic maps merge completely as they are same. Also, reader should note that merge ratio of column *Art of Noise* and row *Base* is defferent that the merge ratio of column *Base* and row *Art of Noise*. Value **20/20** should be interpreted as follows

- Number of merging topics is 20 and
- Number of topics in the row layer is 20.

Thus, all topics in the row topic map merge with a topic in the column layer. One interpretation is that the row topic map is included in the column topic map. However, reader should notice that merging topics may still be different, they may have different occurrences, for example. Value **20/207** is interpreted similarly:

- Number of merging topics between layers is 20 and
- Number of topics in the row topic map is 207.

Looking from this perspective, it is clear that the row topic map has many more topics than merging ones.