you should not use all variables as id.vars
try this code
dfm <- melt(df, id.vars=c("iteration"))
What do you really need to plot?? What is your x and y axis? line plot or point? As far as i
understood this should work.
ggplot(dfm,aes(iterartion,value,colour=variable))+geom_point()
solved how to plot with ggplot?