Predicting your height (like it's 1885)

I wanted to know how my parents' heights translated to mine, so I made this Shiny app: http://melissatan.shinyapps.io/ddp-shiny.

The app takes in your input:

• How tall your parent (either mother or father) is
• Your gender

And produces its estimate of how tall you are likely to be.

It also plots your estimated height against actual parent-child height data, so you'll know how you stack up.

The app uses data collected by Galton, who took the heights of 928 children and their 205 parents in 1885. I've converted it from inches to centimeters. Galton converted female heights to male heights by multiplying them with 1.08, which I will follow.

library(UsingR); data(galton)
galton.m <- galton * 2.54 # inch to cm multiplier
head(galton.m)

    child parent
1 156.718 179.07
2 156.718 173.99
3 156.718 166.37
4 156.718 163.83
5 156.718 162.56
6 157.988 171.45

I fit a linear model on the data to estimate a child's height based on the parent's.

input.height <- 160 # parent height
input.parent <- "mother" # parent gender
input.gender = "male" # child gender
multiplier <- 1; divisor <- 1
if (input.parent == "mother") { multiplier <- 1.08 }
if (input.gender == "female") { divisor <- 1.08}
result <- predict(fit, newdata=data.frame(parent=input.height*multiplier))
result/divisor # convert for child gender

       1 
172.4905