gam_dev_exp: Variable importance for GAMs
In jpwrobinson/funk: James Robinson's functions, attributed where stolen

Function builds GAM and calculates deviance explained by each covariate. Simon Wood; http://r.789695.n4.nabble.com/variance-explained-by-each-term-in-a-GAM-td836513.html Litzow et al. (2013) Reassessing regime shifts in the North Pacific: incremental climate change and commercial fishing are necessary for explaining decadal-scale biological variability. Global Change Biology.

gam_dev_exp(
  dataset,
  exp.names,
  indicator,
  family,
  base_k = -1,
  smoother = "cr"
)

`dataset`	is the dataset containing y and all x covariates. should be scaled and centered (mean = 0, sd = 1)
`exp.names`	= explanatory covariate names, passed as vector of characters
`indicator`	= y variable of interest (character)
`family`	= GAM family distribution, takes 'gaussian' or 'Gamma'
`base_k`	= number of knots for each smoother term. Default = -1, mgcv uses generalized cross-validation
`smoother`	= cubic regression spline method (cr is default)