ggplot error using rmarkdown - object ´percent´ not found - r

Question

So I have been making this scatterplot using ggplot in R.
By using this code as listed below in a regular r script in RStudio I am able to produce the plot that I want to without any errors.
The problem is when I am trying to use the same code in a chunk using rmarkdown to knit to PDF.
I get an error saying: Error in check_breaks_labels(breaks, labels): object percent not found.
Any suggestions? Hope the reproducable example is ok.
library(tidyquant)
library(timetk)
library(ggplot2)
SPY <- tq_get("SPY", from = '2010-01-01',
to = "2020-04-04",
get = "stock.prices")
FXI <- tq_get("FXI", from = '2010-01-01',
to = "2020-04-04",
get = "stock.prices")
QQQ <- tq_get("QQQ", from = '2010-01-01',
to = "2020-04-04",
get = "stock.prices")
SPY_monthly_returns <- SPY %>%
tq_transmute(select = adjusted,
mutate_fun = periodReturn,
period = "monthly",
col_rename = "SPY_ret")
FXI_monthly_returns <- FXI %>%
tq_transmute(select = adjusted,
mutate_fun = periodReturn,
period = "monthly",
col_rename = "FXI_ret")
QQQ_monthly_returns <- QQQ %>%
tq_transmute(select = adjusted,
mutate_fun = periodReturn,
period = "monthly",
col_rename = "QQQ_ret")
SPY_monthly_mean_ret <- SPY_monthly_returns %>%
select(SPY_ret) %>%
.[[1]] %>%
mean(na.rm = TRUE)
FXI_monthly_mean_ret <- FXI_monthly_returns %>%
select(FXI_ret) %>%
.[[1]] %>%
mean(na.rm = TRUE)
QQQ_monthly_mean_ret <- QQQ_monthly_returns %>%
select(QQQ_ret) %>%
.[[1]] %>%
mean(na.rm = TRUE)
SPY_monthly_sd_ret <- SPY_monthly_returns %>%
select(SPY_ret) %>%
.[[1]] %>%
sd()
FXI_monthly_sd_ret <- FXI_monthly_returns %>%
select(FXI_ret) %>%
.[[1]] %>%
sd()
QQQ_monthly_sd_ret <- QQQ_monthly_returns %>%
select(QQQ_ret) %>%
.[[1]] %>%
sd()
d <- data.frame(meanret = c(SPY_monthly_mean_ret,FXI_monthly_mean_ret,QQQ_monthly_mean_ret), sd = c(SPY_monthly_sd_ret,FXI_monthly_sd_ret,QQQ_monthly_sd_ret), names = c("SPY","FXI","QQQ"))
ggplot(d, aes(sd,meanret, color= ticker)) +
geom_point(size=1) + geom_text(aes(label=names)) +
ggtitle("Monthly Risk-Return Plot") + xlab("Volatility") +
ylab("Mean Return") + theme_bw() +
scale_y_continuous(label = percent, limits = c(0, 0.02)) +
scale_x_continuous(label = percent, limits = c(0, 0.08))

Answer 1

The solution was to require(scales) and after that specify "ticker" as I had not done that in my code chunk.
Both were suggested really quickly which is very helpful to me who is learning while writing my bachelor thesis. Thanks a lot!

Answer 2

You forgot to quote percent.
ggplot(d, aes(sd,meanret, color= ticker)) +
geom_point(size=1) + geom_text(aes(label=names)) +
ggtitle("Monthly Risk-Return Plot") + xlab("Volatility") +
ylab("Mean Return") + theme_bw() +
scale_y_continuous(label = "percent", limits = c(0, 0.02)) +
scale_x_continuous(label = "percent", limits = c(0, 0.08))
When not using quotes, ggplot is looking for an object named percent that should hold a string. Because of this, you could also do
p <- ggplot(...)
mylabel = "This is my label"
p + scale_x_continuous(label = "mylabel", limits = c(0, 0.08))