MDS Projection

This node maps data of a high dimensional space onto a lower (usually 2 or 3) dimensional space with respect to a set of fixed data points. Therefore modified Sammons mapping is applied, which iteratively decreases the difference of the distances of high and low dimensional data. When adjusting the position a low dimensional data point by default not its neighbors (or all other data points) are taken into account but a specified set of fixed data points which are not modified. Additionally the data points (and not only the fixed points) can be taken into account when adjusting its positions, therefore the setting "Project only" has to be unchecked. If the setting is checked the data points will be mapped only with respect to the fixed data, which we call a projection. The algorithm converges like a common mds algorithm due to a decreasing learning rate.

Options

Epochs

Specifies the number of epochs to train.

Output dimensions

Specifies the dimension of the mapped output data.

Learning rate

Specifies the learning rate to use. The learning rate is decreased automatically over the trained epochs.

Random seed

Specifies the random seed to use, which allows to reproduce a mapping even if the initialization is done randomly.

Distance metric

Select the distance metric to use for computing distances between data points.

• Euclidean: The straight-line distance between two points in n-dimensional space (L2 norm).
• Manhattan: The sum of absolute differences between coordinates (L1 norm).

Project only

If checked the input data is mapped only with respect to the specified fixed data points (see section 'Fixed Data'). If unchecked, the other (not fixed) data points are taken into account too, when adjusting the position of each single data point.

Use all rows

If enabled, all rows in the input table will be used for the MDS computation. If disabled, only the specified number of rows will be used.

Number of rows to use

Specifies the number of rows to apply the MDS on.

Always include all columns

If checked, node behaves as if all columns were moved to the "Include" list.

Columns to project

Specifies the columns to use by the mapping.

Fixed columns

Specifies the columns to use as fixed data. Be aware that the chosen columns represent the lower dimensional data which is used to project the input data at. The number of columns to choose has to be equal to the value set for output dimension.

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