Bias of estimates through jackknife

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Computes a cumulative multiplicative bias factor that increases (or decreases) systematically over the years in an FLQuant. Starting from 1, each subsequent year is multiplied by 1 + bias, producing a trend that can represent, e.g., a gradually increasing observation bias.

Usage

# S4 method for class 'FLQuantJK'
bias(x)

# S4 method for class 'FLParJK'
bias(x)

bias(object, bias = 0.02)

Arguments

x: An object holding estimates obtained through jackknife
object: An FLQuant whose year dimension and dimnames are used.
bias: Numeric; per-year fractional bias; defaults to 0.02 (2\ year).

Value

A value for the mean bias

An FLQuant with the same dimnames as object containing the cumulative bias multipliers.

Details

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$$\widehat{Bias}_{(\theta)} = (n - 1)((\frac{1}{n}\sum\limits_{i=1}^n\hat{\theta}_{(i)})-\hat{\theta})$$

Author

The FLR Team

Examples


flq <- FLQuant(1:8)
flj <- jackknife(flq)
bias(flj)
#> An object of class "FLQuant"
#> iters:  8 
#> 
#> , , unit = unique, season = all, area = unique
#> 
#>      year
#> quant 1       2       3       4       5       6       7       8      
#>   all 1.02(0) 1.04(0) 1.06(0) 1.08(0) 1.10(0) 1.13(0) 1.15(0) 1.17(0)
#> 
#> units:  NA