Programmatically position ggplot labels - r

Question

I am creating a lot of charts programmatically in R using ggplot2 and have everything working perfectly except the position of bar labels.
This requires inputs of the plot height, y axis scale and text size.
Example (stripped down) plot code:
testInput <- data.frame("xAxis" = c("first", "second", "third"), "yAxis" = c(20, 200, 60))
# Changeable variables
yMax <- 220
plotHeight <- 5
textSize <- 4
# Set up labels
geomTextList <- {
textHeightRatio <- textSize / height
maxHeightRatio <- yMax / height
values <- testInput[["yAxis"]]
### THIS IS THE FORMULA NEEDING UPDATING
testInput[["labelPositions"]] <- values + 5 # # Should instead be a formula eg. (x * height) + (y * textSize) + (z * yMax)?
list(
ggplot2::geom_text(data = testInput, ggplot2::aes_string(x = "xAxis", y = "labelPositions", label = "yAxis"), hjust = 0.5, size = textSize)
)
}
# Create plot
outputPlot <- ggplot2::ggplot(testInput) +
ggplot2::geom_bar(data = testInput, ggplot2::aes_string(x = "xAxis", y = "yAxis"), stat = "identity", position = "dodge", width = 0.5) +
geomTextList +
ggplot2::scale_y_continuous(breaks = seq(0, yMax, yInterval), limits = c(0, yMax))
ggplot2::ggsave(filename = "test.png", plot = outputPlot, width = 4, height = plotHeight, device = "png")
I have tried various combinations of coefficients for the formula, but suspect that at leat one of the factors isn't linear. If this is purely a statistical problem, I could take it to Cross-Validation, but I wondered whether anyone had already solved this?

Answer 1

If your problem is with offsetting the text to not overlap the bar while dealing with varying text sizes, just use vjust which is already proportional to the text size. A value of 0 will make the bottom of the text touch the bar, and a small negative value will give you some space between them:
testInput <- data.frame("xAxis" = c("first", "second", "third"), "yAxis" = c(20, 200, 60))
# Changeable variables
yMax <- 220
plotHeight <- 5
textSize <- 4
# Set up labels
geomTextList <- {
values <- testInput[["yAxis"]]
testInput[["labelPositions"]] <- values # Use the exact value
list(
ggplot2::geom_text(
data = testInput,
# vjust provides proportional offset
ggplot2::aes_string(x = "xAxis", y = "labelPositions", label = "yAxis"),
hjust = 0.5, vjust = -0.15, size = textSize
)
)
}
# Create plot
outputPlot <- ggplot2::ggplot(testInput) +
ggplot2::geom_bar(data = testInput, ggplot2::aes_string(x = "xAxis", y = "yAxis"), stat = "identity", position = "dodge", width = 0.5) +
geomTextList +
ggplot2::scale_y_continuous(limits = c(0, yMax))
ggplot2::ggsave(filename = "test.png", plot = outputPlot, width = 4, height = plotHeight, device = "png")