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

[Troels Ring]

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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