dist_between_2_sigs: Compute the distance between two fatty acid signatures
In qfasar: Quantitative Fatty Acid Signature Analysis in R

Description Usage Arguments Value Details References

The utility function dist_between_2_sigs computes the distance between two fatty acid signatures.

1	dist_between_2_sigs(sig_1, sig_2, dist_meas = 1, gamma = 1)

`sig_1, sig_2`	Equal-length numeric vectors of fatty acid signature proportions.
`dist_meas`	An integer indicator of the distance measure to compute. Default value 1.
`gamma`	The power parameter of the chi-square distance measure. See Details. Default value 1.

The selected distance between the two signatures.

This is an internal utility function. The signatures in sig_1 and sig_2 are presumed to be ready for analysis, which is best accomplished by a call to the function prep_sig. Consequently, to increase execution speed during simulations, no numeric error checking is performed. Please refer to documentation for the function prep_sig for additional details.

If the argument dist_meas is not one of the following integers, a value of NA is returned:

dist_meas == 1 yields the Aitchison distance measure (Stewart et al. 2014). This is the default value.
dist_meas == 2 yields the Kullback-Leibler distance measure of Iverson et al. (2004).
dist_meas == 3 yields the chi-square distance measure (Stewart et al. 2014).

The argument gamma is only used if dist_meas == 3 and need not be passed otherwise. If dist_meas == 3, gamma must be greater than 0 and cannot exceed 1. If dist_meas == 3 and a value for gamma is not passed, a default value of 1 is used.

Iverson, S.J., C. Field, W.D. Bowen, and W. Blanchard. 2004. Quantitative fatty acid signature analysis: A new method of estimating predator diets. Ecological Monographs 74:211-235.

Stewart, C., S. Iverson, and C. Field. 2014. Testing for a change in diet using fatty acid signatures. Environmental and Ecological Statistics 21:775-792.

qfasar documentation built on March 20, 2020, 1:10 a.m.