Description Usage Arguments Value Author(s) References Examples

This function finds the set of most dissimilar rows in a data matrix. If no initial selection is presented, the first object is selected by comparison with the vector of column means. As a distance function the determinant of the crossproduct matrix is used.

1 |

`x` |
Data matrix (numerical). May not contain missing values. |

`ncomp` |
Number of rows to be selected. |

`initXref` |
Optional matrix to be expanded - should be a subset of the rows to select. |

The function returns a submatrix of X, where the columns contain the (unit-length scaled) spectra from the input data that are most dissimilar.

Ron Wehrens

F. Questa Sanchez et al.: Algorithm for the assessment of peak purity in liquid chromatography with photodiode-array detection. Analytica Chimica Acta 285:181-192 (1994)

R. Wehrens: Chemometrics with R. Springer Verlag, Heidelberg (2011)

1 2 3 4 5 6 7 8 9 10 11 12 13 | ```
data(tea)
tea <- lapply(tea.raw, preprocess, maxI = 100)
ncomp <- 7
spectra <- opa(tea, ncomp)
myPalette <- colorRampPalette(c("black", "red", "blue", "green"))
mycols <- myPalette(ncomp)
matplot(as.numeric(rownames(spectra)), spectra, type = "l", lty = 1,
xlab = expression(lambda), ylab = "", col = mycols)
legend("topright", legend = paste("Comp.", 1:ncomp), col = mycols,
lty = 1, ncol = 2, bty = "n")
``` |

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