Running code one line at a time breaks inline chunk output - r

Question

When I run a complete chunk of code, inline output appears as expected. However if I run the same chunk one line at a time it breaks if I use more than one plot call. So:
set.seed(129485)
x=1:10
y=rnorm(length(x), x, 1)
plot(x,y)
lines(x,y)
works fine in an R script. If I insert it into a code chunk in a brand new R markdown file, like this:
---
title: "wtf"
author: "Drew Tyre"
date: "December 22, 2016"
output: html_document
---
```{r}
set.seed(129485)
x=1:10
y=rnorm(length(x), x, 1)
plot(x,y)
lines(x,y)
```
This chunk runs if I run the entire chunk using control-shift-enter, the play button, or by selecting all the lines and using control-enter. However, if I run the lines one at a time using control-enter, it breaks on the call to lines(x,y):
Error in plot.xy(xy.coords(x, y), type = type, ...) : plot.new has not been called yet
It goes away if I set the options to chunk output in console. I guess it could be the intended behavior, but then maybe control-enter should do the same thing as control-shift-enter when using inline output?
I'm using RStudio 1.0.44 and
R version 3.3.2 (2016-10-31)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows >= 8 x64 (build 9200)
locale:
[1] LC_COLLATE=English_United States.1252
[2] LC_CTYPE=English_United States.1252
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C
[5] LC_TIME=English_United States.1252
attached base packages:
[1] stats graphics grDevices utils datasets
[6] methods base
loaded via a namespace (and not attached):
[1] rsconnect_0.4.3 tools_3.3.2 yaml_2.1.14
[4] knitr_1.15.1
I can also reproduce this behavior on this machine:
R version 3.2.3 (2015-12-10)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 7 x64 (build 7601) Service Pack 1
locale:
[1] LC_COLLATE=English_United States.1252
[2] LC_CTYPE=English_United States.1252
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C
[5] LC_TIME=English_United States.1252
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] tools_3.2.3 knitr_1.12.3

Answer 1

Kevin Ushey over at the RStudio community forum had this answer:
This is unfortunately a consequence of the Notebook execution model. The graphics device state is reset after each execution, so code execution that is done line-by-line (e.g. to fill a plot) will not work as expected.
There are some workarounds for this:
Prefer executing a whole chunk at a time, using e.g. Cmd + Shift + Enter,
Wrap your plot generating code in brackets {},
Define a function that generates the entire plot,
Disable inline chunk output for that document. (Do this by clicking the Gear icon in the source toolbar and choosing 'Chunk Output in Console')