Variable plot height within single chunk - r

Question

The following knitr thingy produces multiple plots via lapply. Their number and content therefore varies depending on the preceding R code.
Is there a way to set the plot height individually for each plot using a variable (like the height of the highest bar in a given bar chart)?
---
title: "Variable plot height"
output: word_document
---
Plots:
```{r, echo=FALSE, fig.height = 2}
library(ggplot2)
library(tidyr)
data(mtcars)
mtcars$car = row.names(mtcars)
cars = gather(mtcars[1:5, ], variable, value,
-c(car, mpg, disp, hp, qsec))
lapply(unique(cars$car), function(x) {
ggplot(cars[cars$car == x, ], aes(variable, value)) +
geom_bar(stat = "identity")
})
```

Answer 1

One way would be to create each image and include it into the document as an external image. You can employ the power of "asis". Here's a small example.
---
title: "Untitled"
author: "Neznani partizan"
date: "04. december 2015"
output: html_document
---
```{r, echo=FALSE, fig.height = 2}
library(ggplot2)
library(tidyr)
data(mtcars)
mtcars$car = row.names(mtcars)
cars = gather(mtcars[1:5, ], variable, value,
-c(car, mpg, disp, hp, qsec))
suppressMessages(invisible(lapply(unique(cars$car), function(x) {
ggplot(cars[cars$car == x, ], aes(variable, value)) +
geom_bar(stat = "identity")
ggsave(sprintf("%s.png", x))
})))
```
```{r results = "asis", echo = FALSE}
cat(sprintf("<img src='%s' alt='' style='width:350px;height:228px;'> <br />",
list.files(pattern = ".png", full.name = TRUE)))
```
Image sizes can be adjusted on-the-fly using appropriate arguments in ggsave and/or in printing HTML code.

Answer 2

The fig.width and fig.height chunk options can take in multiple values. In your example, there are five plots, so by setting a numeric vector of length five for the widths and heights, and saving the list of ggplot objects, you can have one chunk produce five graphics of different sizes in the final document. An example .Rmd file is below.
---
title: "Variable plot height"
output: word_document
---
Plots:
```{r, echo=FALSE}
library(ggplot2)
library(tidyr)
data(mtcars)
mtcars$car = row.names(mtcars)
cars = gather(mtcars[1:5, ], variable, value, -c(car, mpg, disp, hp, qsec))
plots <-
lapply(unique(cars$car), function(x) {
ggplot(cars[cars$car == x, ], aes(variable, value)) +
geom_bar(stat = "identity")
})
widths <- c(3, 4, 5, 3, 6)
heights <- c(3, 3, 3, 4, 3)
```
```{r show_plots, fig.width = widths, fig.height = heights}
plots
```