tauW {aqp} | R Documentation |

`tauW`

: Computes: (1) unweighted naive, (2) weighted naive, (3) unweighted *tau*, (4) weighted *tau* accuracy statistics

tauW( CM, W = diag(sqrt(length(as.matrix(CM)))), P = rep(1/nrow(as.matrix(CM)), nrow(as.matrix(CM))) )

`CM` |
a square confusion (cross-classification) matrix (rows: allocation, columns: reference) |

`W` |
weights: 1 on diagonals, [-1..1] off giving partial credit to this error |

`P` |
prior probability vector, length = number of rows/columns in |

`summaryTauW`

: prints a summary of the results from *tauW*

`xtableTauW`

: formats a LaTeX table with results from *tauW* and saves it as a `.tex`

file for import into a LaTeX document.

Input matrices `CM`

and `W`

may be in `data.frame`

format and will be converted

Weights matrix `W`

: 0 = no credit; 1 = full credit; -1 = maximum penalty

If absent, default is no partial credit, i.e., unweighted.

Prior probabilities vector `P`

: If absent, `P`

are equal priors for each class. Special value `P = 0`

is interpreted as `P`

= column marginals.

Error checks: `CM`

must be square; `P`

must have correct number of classes and sum to 1 +/- 0.0001; `W`

& `CM`

must be conformable

Results are returned in a list with obvious R names

D G Rossiter

Rossiter, D. G., Zeng, R., & Zhang, G.-L. (2017). Accounting for taxonomic distance in accuracy assessment of soil class predictions. Geoderma, 292, 118–127. doi: 10.1016/j.geoderma.2017.01.012

Ma, Z. K., & Redmond, R. L. (1995). Tau-coefficients for accuracy assessment of classification of remote-sensing data. Photogrammetric Engineering and Remote Sensing, 61(4), 435–439.

Naesset, E. (1996). Conditional tau coefficient for assessment of producer’s accuracy of classified remotely sensed data. ISPRS Journal of Photogrammetry and Remote Sensing, 51(2), 91–98. doi: 10.1016/0924-2716(69)00007-4

# example confusion matrix # rows: allocation (user's counts) # columns: reference (producer's counts) crossclass <- matrix(data=c(2,1,0,5,0,0, 1,74,2,1,3,6, 0,5,8,6,1,3, 6,1,3,91,0,0, 0,4,0,0,0,4, 0,6,2,2,4,38), nrow=6, byrow=TRUE) row.names(crossclass) <- c("OP", "SA", "UA", "UC", "AV", "AC") colnames(crossclass) <- row.names(crossclass) # build the weights matrix # how much credit for a mis-allocation weights <- matrix(data=c(1.00,0.05,0.05,0.15,0.05,0.15, 0.05,1.00,0.05,0.05,0.05,0.35, 0.05,0.05,1.00,0.20,0.15,0.15, 0.15,0.05,0.25,1.00,0.10,0.25, 0.05,0.10,0.15,0.10,1.00,0.15, 0.20,0.30,0.10,0.25,0.20,1.00), nrow=6, byrow=TRUE) # unweighted accuracy summaryTauW(nnaive <- tauW(crossclass)) # unweighted tau with equal priors, equivalent to Foody (1992) modified Kappa tauW(crossclass)$tau # unweighted tau with user's = producer's marginals, equivalent to original kappa (priors <- apply(crossclass, 2, sum)/sum(crossclass)) tauW(crossclass, P=priors)$tau # weighted accuracy; tau with equal priors summaryTauW(weighted <- tauW(crossclass, W=weights)) # weighted accuracy; tau with user's = producer's marginals summaryTauW(tauW(crossclass, W=weights, P=priors)) # change in accuracy statistics weighted vs. non-weighted (weighted$overall.weighted - weighted$overall.naive) (weighted$user.weighted - weighted$user.naive) (weighted$prod.weighted - weighted$prod.naive)

[Package *aqp* version 1.31 Index]