r - How to add dynamic column name to subset?

Question

this is part of shiny app, those values came from reactive ui/server, I narrowed down my problem in server.R, and I work with this plain R for simplicity, it should reflect my question correctly I hope, how to make this line with <@><< work ??? I also tried, noquote, eval and nothing.

t <- data.frame(Titanic)
inputparam = "Class"
inputvalue = "2nd"
c(inputparam, "=",inputvalue)
noquote(inputparam)

head(subset(t, Class ==inputvalue))   ## works OK
head(subset(t, inputparam ==inputvalue))   ## <@>><   doesn't work !!!!!
#temp <- quote(inputparam)
#head(subset(t,  eval(temp) == inputvalue)) 

Answer 1

eval with parse works

eval(parse( text=paste0("subset(t, ", inputparam, "=='", inputvalue, "')") ))

The inputvalue has to be enclosed as with another quote so that parse recognizes it as a character.

Alternatively you should try something like this, (check comments for reasons)

t[ t[colnames(t)==inputparam]==inputvalue, ]