RStudio on Windows can't use UTF-8 symbol (approx equal ≈) in data frame

I am trying to add a "≈" to a data frame.

You can add symbols like "+" and "-" to a data frame.
You can even add the ≈ symbol to a plot using

text(x,y, expression(""%~~%"")) 

but this won't work inside a data frame and I cannot find a way to do this.
I have tried just pasting a ≈ using paste("≈") and a few other equally feeble things.
For example:

x <- "≈"
print(x)

[1] "˜"

Here is a small example. The only difference that I would like to see is those middle two rows become ≈

df<-data.frame(prop=c(0.99, 0.97, 0.5,0.4,0.01, 0.02), symbol=NA)

df$symbol<-ifelse(df$prop>=0.95, "+","")
df$symbol<-ifelse(df$prop<=0.05, "-",df$symbol)
df$symbol<-ifelse(df$prop<=0.95 & df$prop>=0.05, "approximately equal symbol here",df$symbol)

df`

looks like

 prop                          symbol
1 0.99                               +
2 0.97                               +
3 0.50 approximately equal symbol here
4 0.40 approximately equal symbol here
5 0.01                               -
6 0.02                               -                              -

What I would like

 prop       symbol
1 0.99        +
2 0.97        +
3 0.50        ≈
4 0.40        ≈
5 0.01        -
6 0.02        -  

as per the comments

Sys.setlocale(locale='.utf8') or Sys.setlocale(locale='.65001')