R Markdown not displaying plotly graphics - r

Question

I am using Rstudio Version 1.1.447. on a Dell Latitude E5470 using Windows 10. I am trying to create a presentation for an assignment using R markdown and knittr and ioslides. The resultant presentation has a complete black page instead of the graph. The graph however does display in Rstudio if I run the code on its own outside of R markdown.
Here is my code:
```{r, echo = TRUE, include=FALSE}
library("plotly")
library("ggplot2")
library("datasets")
data("state")
x <- state.area
y <- state.x77[,1]*1000
z <- state.x77[,5]
fac <- state.division
newdf <- as.data.frame(cbind(state.area, state.x77[,1]*1000, state.x77[,5], state.division))
colnames(newdf) <- c("Area", "Population", "Murder", "Division")
p <-plot_ly(newdf,
x="Area",
y="Population",
z="Murder",
type="scatter3d",
mode="markers",
color="Division")
p
```

Answer 1

Try the same but removing the {r, echo = TRUE, include=FALSE} and replace it with just {r}.
Here is a complete working answer.
---
title: "Plotly in Markdown Example"
output: html_document
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
library("plotly")
library("ggplot2")
library("datasets")
data("state")
x <- state.area
y <- state.x77[,1]*1000
z <- state.x77[,5]
fac <- state.division
```
## Plot title goes here
Awesome comments about plot output goes here:
```{r}
newdf <- as.data.frame(cbind(state.area, state.x77[,1]*1000, state.x77[,5], state.division))
colnames(newdf) <- c("Area", "Population", "Murder", "Division")
p <-plot_ly(newdf,
x="Area",
y="Population",
z="Murder",
type="scatter3d",
mode="markers",
color="Division")
p
```