RNLM Process

• RNLM Process
• • Process Overview
  • • File Handling
    • Iteration Procedure
  • Input Files
  • Output Files
  • Fields
  • Parameters
  • Example

To access this process:

• Sample Analysis ribbon >> Statistics >> Geochemical Processes >> R Mode Non Linear Mapping.

• Enter "RNLM" into the Command Line and press <ENTER>.

• Display the Find Command screen, locate RNLM and click Run.

See this process in the Command Table.

Process Overview

R - mode non linear mapping groups together elements using the angular distances calculated from the Pearsson correlation coefficient matrix.

Note the difference with Q mode non linear mapping which clusters samples on the basis of composition.

A two dimensional view of the element clusters, or the scores NLM-X versus NLM-Y, is calculated to represent them as they would appear in multi-dimensional space on the basis of element similarity between pairs of samples. All input data is standardized prior to the calculation of the correlation matrix and the linear mapping output scores are normalized prior to plotting.

R - mode non linear mapping, when compared with R - mode factor analysis, is more sophisticated and does not distort or sub-divide the element or parameter clusters. Non linear mapping will give more separable clusters than other hierarchical techniques such as R - mode cluster analysis.

Note: There is a restriction of 2000 samples.

File Handling

The input file &(IN) must have a separate identifier field (*SAMPID). The output file &(SCORES) contains three parameters, FIELD the field identifier, NLM-X and NLM-Y the output scores for plotting the multi-dimensional inter-element distances as a two dimensional flat plane. Results can be displayed using QUIG, PLOTDA or PLOTAN.

Iteration Procedure

In order to present a two dimensional view of multi-dimensional space with minimum distortion of the sample clusters, the calculated mapping error has to be minimized by an iterative method (steepest descent). This is controlled by the @CONVLIM parameter, that is the minimum difference allowed in the mapping error between iterations, @MAXIT, the maximum number of iterations permitted and the @MAGIC parameter which specifies the stepping function used for each iteration. If the stepping function @MAGIC is decreased, the number of iterations is increased with an obvious time penalty on the length of the calculation. The value used must be taken into account when there are a large number of samples. However the results can be more stable.

Input Files

Output Files

Fields

Parameters

Example

!RNLM    &IN(AEG2),@SCORES(RSCORES),@SAMPID='ID',
@CONVLIM=0.0001,@MAGIC=0.35,@PRINT=1

Related topics and activities

• QNLM Process

• QUIG Process

• PLOTDA Process

• PLOTAN Process