How to print all recorded plots in a list in R Markdown - r

Question

this is my first question at StackOverflow. If I am doing something wrong let me know to improve the next questions.
I am starting with R Markdown and I have some troubles to print recorded plots with a for loop. Well, before I run Rmarkdown file, I run R function that generate a list of several data frames and plots.
To make it easier I put here a simplified reproducible example of this list just with plot objects.
x <- c(1,2,3,4,5)
y <- c(1,2,3,4,5)
plot(x,y)
abline(h=1)
p1.1 <- recordPlot()
plot(x,y)
abline(h=3)
p1.2 <- recordPlot()
plot(x,y)
abline(h=4)
p2.1 <- recordPlot()
plot(x,y)
abline(h=6)
p2.2 <- recordPlot()
lista<-NULL
lista["p1.1"] <- list(p1.1)
lista["p1.2"] <- list(p1.2)
lista["p2.1"] <- list(p2.1)
lista["p2.2"] <- list(p2.2)
save(new_list, file = "Data.RData")
Then I load this list in R Markdown file like this:
```{r setup}
knitr::opts_chunk$set(echo = TRUE,fig.keep = "all")
load("Data.RData")```
And I try to print this plots like this:
```{r,echo=FALSE, results='asis',fig.keep='all'}
for (i in c(1,2)){
for(j in c(1,2)){
print(lista[[paste(paste("p",i,sep=""),j,sep=".")]])
}
}```
When I run Knitr to obtain HTML file the result is that just the last plot of the for loop is shown.
I have tried use lapply instead of for loop, but it did not work for me. Also I tried to use replayPlot function print(replayPlot(lista[[paste(paste(paste("p",i,sep=""),".",sep=""),j,sep="")]])) with the same result.
Is there any way to solve this without modifying the previous R function that generate the plot list?
Thank you for the answers.

Answer 1

The syntax you use would probably be OK with a list of ggplot objects, but with base plot objects, you need to call plot.new() so that the next plot in the list doesn't overwrite the previous one:
---
title: "test"
output: html_document
---
## Define plots
```{r}
x <- c(1,2,3,4,5)
y <- c(1,2,3,4,5)
plot.new()
plot(x,y)
abline(h=1)
p1.1 <- recordPlot()
plot.new()
plot(x,y)
abline(h=3)
p1.2 <- recordPlot()
plot.new()
plot(x,y)
abline(h=4)
p2.1 <- recordPlot()
plot.new()
plot(x,y)
abline(h=6)
p2.2 <- recordPlot()
lista<-NULL
lista["p1.1"] <- list(p1.1)
lista["p1.2"] <- list(p1.2)
lista["p2.1"] <- list(p2.1)
lista["p2.2"] <- list(p2.2)
```
# Print list
```{r,echo=F}
for (i in c(1,2)){
for(j in c(1,2)){
# Needed to avoid overwrite
plot.new()
print(lista[[paste(paste("p",i,sep=""),j,sep=".")]])
}
}
```
Note that you can simplify the syntax of the loops:
for(p in lista) {
plot.new()
print(p)
}

Answer 2

You don't need a loop to plot each ggplot saved in a list. Much simpler:
```{r,echo=FALSE}
print(lista)
```
This automatically plots every element of the list (each plot) to the Markdown.