Question

I’m not having any success combining lapply, substitute, print, plot, and list in a function statement. Can someone direct me to a way to revise this code? I’d like to:

1. automate plotting some but not all fields in a data frame vs. the first field in the df
2. specify the fields to plot
3. write the result to a file

The fields are numeric. Thanks.

brg<-as.data.frame(sqlFetch(channel,"Bearing"))               
is.data.frame(brg)                                            

varlist<-names(brg)[c(6,8,10,12)]                             
varlist                                                       
pdf(file="brg%d.pdf")                                         
figures<-lapply(varlist,function(x) {                         
print(plot(substitute(brg[c(1,i)], (list(i = as.name(x))))))
})  

update: Thanks for the comments. Here are two working versions of this code with axis lables (df read from SQL Server as written):

     #vers. 1
     brg<-as.data.frame(sqlFetch(channel,"Bearing"))
     is.data.frame(brg)
     dim(brg)
     head(brg)
     names(brg)<-tolower(names(brg))
     names(brg)
     varlist<-names(brg)[c(6,8,10,12)]
     varlist
     pdf(file="brgd.pdf")
     for (x in varlist) plot(brg[,1],brg[,x], xlab=names(brg[1]),ylab=as.name             (x))           
     dev.off()

     #vers. 2
     brg<-as.data.frame(sqlFetch(channel,"Bearing"))
     is.data.frame(brg) 
     dim(brg)
     head(brg)
     names(brg)<-tolower(names(brg))
     names(brg)
     varlist<-names(brg)[c(6,8,10,12)]
     varlist
     pdf(file="brg1.pdf")
     figures<-lapply(varlist,function(x) {

     (plot(brg[,1],brg[,x], ylab=as.name(x)))
     })
     dev.off()                                                 

Answer 1

It is really not clear what you want to do , but I still have some comments about your code. I think here you try to complicate a simple task with , of plotting some variables ans save the plots in a file.

1. No need to use substitute (it will give symbol), you can subset your data.frame with column names.
2. No need to use lapply here since you don’t save the result , just you want to repeat the plot.
3. Why the the use of % in the name of file.

4. You must close the device after plotting to unlock it.

   brg<- data.frame(a=rnorm(10),b= rnorm(10),   ## a reproducible data frame
                    c=rnorm(10))
   varlist<-names(brg)[c(1,2)] 
   pdf(file="brgd.pdf")                                                   
   for (x in varlist)   plot(brg[,1],brg[x])           ## the substitue would give brg[c(1,a)] !!
   dev.off()