```
devtools::install_github("alexpkeil1/qgcompint")
library(qgcomp)
library(qgcompint)
set.seed(40)
dat <- data.frame(y=runif(50),
x1=runif(50),
x2=runif(50),
z=rbinom(50,1,0.5),
r=rbinom(50,1,0.5))
# quantile g-computation without effect measure modification
qfit <- qgcomp.noboot(f=y ~ z + x1 + x2,
expnms = c('x1', 'x2'),
data=dat, q=2,
family=gaussian())
# no output given here
# with effect measure modification by Z
(qfitemm <- qgcomp.emm.noboot(f=y ~ z + x1 + x2,
emmvar="z",
expnms = c('x1', 'x2'),
data=dat, q=2,
family=gaussian()))
> ## Qgcomp weights/partial effects at z = 0
> Scaled effect size (positive direction, sum of positive coefficients = 0)
> None
> Scaled effect size (negative direction, sum of negative coefficients = -0.278)
> x2 x1
> 0.662 0.338
> ## Qgcomp weights/partial effects at z = 1
> Scaled effect size (positive direction, sum of positive effects = 0.0028)
> x1
> 1
> Scaled effect size (negative direction, sum of negative effects = -0.0128)
> x2
> 1
> Mixture slope parameters (Delta method CI):
> Estimate Std. Error Lower CI Upper CI t value Pr(>|t|)
> (Intercept) 0.58062 0.11142 0.36224 0.79900 5.2112 4.787e-06
> psi1 -0.27807 0.20757 -0.68490 0.12876 -1.3397 0.1872
> z -0.10410 0.15683 -0.41148 0.20329 -0.6637 0.5103
> z:mixture 0.26811 0.26854 -0.25822 0.79444 0.9984 0.3235
> Estimate (CI), z=1:
> -0.0099575 (-0.34389, 0.32398)
```

- Single modifiers only (e.g. interaction terms between a modifier and the mixture can only be estimated for a single modifier at a time). This also implies that no interaction terms between the modifier and other covariates can be considered.
- linear only specifications (i.e. linear effects of a mixture, but not covariates) for Cox model

- coefficients
- psi1 coefficient: effect of the mixture in the referent category of
the effect measure modifier (
`z`

in this case) - z coefficient: main effect of the effect measure modifier (will change based on name of effect measure modifier)
- z:mixture coefficient: interaction term between the effect measure modifier and the entire mixture

- psi1 coefficient: effect of the mixture in the referent category of
the effect measure modifier (
- weights/partial effects (only given if effect measure modifier is
binary)
- first set of weights/sum of negative/positive coefficients: -
weights: proportion of positive/negative partial effect in the reference
stratum effect measure modifier (here,
`z=0`

)- partial effect: sum of main term coefficients for exposure in a
given direction (these will sum to psi1, the effect estimate in the
reference stratum effect measure modifier (here,
`z=0`

))

- partial effect: sum of main term coefficients for exposure in a
given direction (these will sum to psi1, the effect estimate in the
reference stratum effect measure modifier (here,
- second set:
- weights: proportion of positive/negative partial effect in the index
stratum effect measure modifier (here,
`z=1`

) - partial effect: sum of main term coefficients + interaction term
coefficients for exposure in a given direction (these will sum to the
mixture effect estimate in the index stratum effect measure modifier
(here,
`z=1`

))

- weights: proportion of positive/negative partial effect in the index
stratum effect measure modifier (here,

- first set of weights/sum of negative/positive coefficients: -
weights: proportion of positive/negative partial effect in the reference
stratum effect measure modifier (here,
- Additional estimates (only given if effect measure modifier is
binary): The effect of the mixture in the index category of the effect
measure modifier (here,
`z=1`

)