Print an rgl plot from each iteration in a for loop to HTML in RMarkdown?

Question

I am trying to print a 3d plot from within a loop in RMarkdown to an HTML.

It is a bit like this question: How to include multiple plot3d in markdown (knitr) under a loop

However, the answers there involve saving the plots from each iteration and then plotting at the end. I am wondering if there is a way to have it "dynamically" print with each iteration.

For example, for 2d base plots or ggplots, you can use print() to dyanmically print within each loop iteration, I wonder if there is anything like that.

Ideally, the code block would allow "result = 'asis'", for dynamic printing of sub-headings.

For example, this is the sort of behaviour I am hoping for:

x <- sort(rnorm(1000))
y <- rnorm(1000)
z <- rnorm(1000) + atan2(x,y)

cols <- c("red", "orange", "green", "blue", "purple")


for(i in 1:3){

  plotlab <- "


# 3D Plot for Sample %s

Here we plot a 3d PCA plot for this sample.


"
  
    cat(sprintf(plotlab, i)) #this prints out a dynamic title if result='asis' is in the code options

    plot3d(x, y, z, col = cols[i])

    print( rglwidget() ) ## this is what I hope to achieve
}

Thank you so much for any help!

Answer 1

rgl is more like leaflet or other HTML widgets than like base plots. Here's an example that plots your 3 plots, with labels between:

```{r}
library(htmltools)
library(rgl)

x <- sort(rnorm(1000))
y <- rnorm(1000)
z <- rnorm(1000) + atan2(x,y)

cols <- c("red", "orange", "green", "blue", "purple")

allplots <- NULL
for (i in 1:3) {
    plotlab <- "3D Plot for Sample %s"

    plotmsg <- "Here we plot a 3d PCA plot for this sample."

    allplots <- tagList(allplots, 
                        h3(sprintf(plotlab, i)),
                        p(plotmsg))

    plot3d(x, y, z, col = cols[i])
  
    allplots <- tagList(allplots, rglwidget())
}
allplots
```

Notice that you don't use cat() to print the labels, you have to generate HTML for them, because all the plotting happens when the allplots object is printed.