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The development of this package is motivated by the water, sanitation, and hygiene (WaSH) data in which we were interested in investigating the contribution of demographic and socio-economic factors to improved WaSH indicators among the slum dwellers in Nairobi, Kenya. We noticed that the predictions we generated using the existing packages consistently over- or under- estimated the observed proportions; and did not align well with the observed data points. In other words, what we call . There are several (challenges) reasons for this, including:

  • the choice of the
  • uncertainty estimation – the choice of for computing confidence intervals
  • biases induced by non-linear averaging due to non-linear transformation in generalized linear models

It implements two approaches for constructing outcome plots (prediction and effect plots). These include:

  • mean-based approach
  • observed-value approach

It can also be used to generate bias-corrected prediction and effect estimates for generalized linear models involving non-linear link functions, including models with random effects. This package complements the existing ones by providing:

  • a straightforward way to generate effects plots
  • a robust way to correct for non-linear averaging bias in generalized (mixed) models


You can install the development version of varpred from GitHub with:

# install.packages("remotes")


We use mtcars data to show outcome plots:

  • isolate=TRUE to generate effect plot
  • isolate=FALSE to generate prediction plot

## Set theme for plots

## Fit the model
mod <- lm(mpg ~ wt + hp, mtcars)

## Effect
ef <- varpred(mod, "wt", isolate=TRUE, modelname="effect")

## Prediction
pred <- varpred(mod, "wt", isolate=FALSE, modelname="prediction")
    + scale_color_brewer(palette = "Dark2")

## Compare effect and prediction
all_v <- combinevarpred(list(ef, pred))
p1 <- plot(all_v)

## Add observed data
    + geom_point(data=mtcars, aes(x=wt, y=mpg), col="grey")
    + labs(colour="Method", linetype="Method")
    + scale_color_brewer(palette = "Dark2")