I am trying to save the graph in PDF format and getting the following error:

plot(data[,2],data[,3],col=color_vector,cex=size_vector/20,pch=19,xlab="range",ylab="column",main="Field effects on plant height")
> pdf("R/eliz/field_effect.pdf")
Error in pdf("R/eliz/field_effect.pdf") : 
  cannot open file 'R/eliz/field_effect.pdf'
> plot(data[,2],data[,3],col=color_vector,cex=size_vector/20,pch=19,xlab="range",ylab="column",main="Field effects on plant height")
> dev.off()

suggestions, Thanks for the help

Typically the path ("R/eliz") doesn't exist or you don't have permission to create a file there.