Randomly subtract or add an amount to a proportion of the grid ratings. This emulates randomness during the rating process, producing a grid which might also have resulted.

## Examples

```
## All results for PVAFF index when ratings are slightly perturbated
p <- indexPvaff(boeker)
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
l <- grids_perturbate(boeker, n = 100, prop = .1)
pp <- sapply(l, indexPvaff) # apply indexPvaff function to all perturbated grids
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
#> Note: As of v0.1.14 PVAFF is derived using PCA of the construct centered ratings by default.Before that the construct correlation matrix was used (see method=2).
#>
range(pp) # min and max PVAFF
#> [1] 0.3674606 0.4375565
hist(pp, xlab = "PVAFF values") # visualize
abline(v = p, col = "blue", lty = 2)
```