Introduction
Multidimensional Scaling is a technique for visualizing distances between objects where the distance is known between the pairs of objects. This article describes how to go from a distance matrix:
To a two-dimensional scatterplot, where each of the objects is represented as a point:
Requirements
A Displayr document containing the distance matrix that you want to use as input to the MDS analysis.
Method 1
1. From the menus, select Anything > Advanced Analysis > Dimension Reduction > Multidimensional Scaling (MDS)
2. In the object inspector under Inputs > Algorithm select MDS - Metric or MDS - Non-metric.
- Metric MDS minimizes the difference between distances in input and output spaces.
- Non-metric MDS aims to preserve the ranking of distances between input and output spaces.
Often we care more about relative positioning than absolute differences, in which case non-metric is preferred to metric MDS. For the example below, I've selected Metric.
3. Under Inputs > Distance Matrix, select your distance matrix object.
4. Click the Calculate button to generate the MDS output.
Method 2
1. From the menus, select Anything > Advanced Analysis > Dimension Reduction > Multidimensional Scaling (MDS)
2. In the object inspector under Inputs > Algorithm select MDS - Metric or MDS - Non-metric. For the example below, I've selected Metric.
3. Under Inputs > Distance Matrix, select Paste or Type Distance Matrix.
4. Enter a symmetrical matrix of distances which should have 0 in the diagonal. For this example, I've entered distances between four Australia cities.
5. Click OK.
6. Click the Calculate button to generate the MDS output.
See Also
How to Create a Distance Matrix
How to do Multidimensional Scaling from a Variables
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