[R] cannot coerce class '"expression"' to a data.frame

[William Dunlap]

Try using the I() function in the call to data.frame.  E.g.,

> d <- data.frame(X=1:3, Y=1:3, Substance=I(expression(H[2]*O, H[2] * O[2],
H*S*O[4])))
> with(d, {plot(X,Y,type="n",xlim=c(0,4)); text(X, Y, Substance)})

Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Sat, Mar 21, 2020 at 1:45 AM Troels Ring <tring using gvdnet.dk> wrote:

> Dear friends - I have some old data of chemical results and want to
> annotate
> the points with chemical formula. If I just do
>
> ID <- c("HCl 7","HCl 5.25","HCl 3.5","HCL 7 no Na","HCl 3.5  No Na",
>
> "HSO4 7 no  Na",
>
>         "HNO3 7 No Na")
>
> I can make a data.frame like
>
> DD <- data.frame(x=1:7,ID)
>
>
>
> and plotting works fine.
>
> But if I try to format sulfuric acid and nitric acid like
>
> ID <- c("HCl 7","HCl 5.25","HCl 3.5","HCL 7 no Na","HCl 3.5  No Na",
>
>         expression(paste(HSO[4]," 7 no  Na")),
>
>         expression(paste(HNO[3]," 7 No Na")))
>
>
>
> DD <- data.frame(x=1:7,ID)
>
> Elicits an error
>
> Error in as.data.frame.default(x[[i]], optional = TRUE) :
>
>   cannot coerce class '"expression"' to a data.frame
>
> and plotting is prohibited - so how is this bypassed?
>
>
>
> I'm on Windows 10,
>
> R version 3.6.1 (2019-07-05)
>
>
>
> All best wishes
>
> Troels Ring, MD
>
> Aalborg, Denmark
>
>
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