Answer by smoe for How to check if object (variable) is defined in R?

There may be situations in which you do not exactly know the name of the variable you are looking for, like when an array of results have been created by a queuing system. These can possibly be addressed with "ls" and its argument "pattern" that expects a regular expression.

The "exists" function could be reimplemented that way as

exists <-function(variablename) {   #print(ls(env=globalenv()))   return(1==length(ls(pattern=paste("^",variablename,"$",sep=""),env=globalenv())))}

While preparing this answer, I was a bit surprised about the need for the need of the specification of the environment when invoking ls() from within a function. So, thank you for that, stackoverflow! There is also an "all.names" attribute that I should have set to true but have omitted.