R help - Jul 2021 - assign a data frame name from a list in do loop

Hello List,
I wrote a script below to compare the difference of data frames structure (and
will do something else). First of all I save the file list in a data frame ora,
then I use for loop to 1. load the data from two resource, 2. generate data
structure into two data frames, 3.do the comparesion of the two data frames of
data structure and put it into a data frame, 4. remove the useless data frames
for next loop
for (j in 1:nrow(ora))
{
? mycol? <- ora[j,"fname"]
#--------------------work on csv------------??
? mycsv? <- paste0(mycol,".csv")
? rdcsv? <- noquote(paste0("w:/project/_Joe.B/Oracle/data/",
mycsv))
? rr? ? ?<- read.csv(rdcsv)

#--------------------work on SS ------------??
? myss? ?<- paste0("gemd.", mycol)
? rdss? ?<- paste0('select * from ',myss)
? ss? ? ?<- dbGetQuery(con, rdss)
??
#--------------------compare DF structure? ?------------??
str_rr <- as.data.frame(summary.default(rr))
str_ss <- as.data.frame(summary.default(ss))


sdif_[j] <- sqldf('select * from str_rr except select * from str_ss')

#---------remove data frame from memory--------------

? rm(rr)
? rm(ss)
? rm(str_rr)
? rm(str_ss)
}
In the step 3, I want to use ora$fname in the loop to?assign a data frame name.
So, I will look the output later. But?sdif_[j] doesn't work for this. Can
someone help me to fix this part?
Thanks,
Kai
	[[alternative HTML version deleted]]

Hello,

Just before for(j in 1:nrow(ora)) include the following code line (I 
have removed the underscore):

sdif <- vector("list", length = nrow(ora))


In the loop:

sdif[[j]] <- sqldf(etc)



Also, once again, why noquote? It's better to form file names with 
file.path:


rdcsv? <- file.path("w:/project/_Joe.B/Oracle/data", mycsv)


Hope this helps,

Rui Barradas


?s 16:55 de 14/07/2021, Kai Yang via R-help escreveu:
> Hello List,
> I wrote a script below to compare the difference of data frames structure
(and will do something else). First of all I save the file list in a data frame
ora, then I use for loop to 1. load the data from two resource, 2. generate data
structure into two data frames, 3.do the comparesion of the two data frames of
data structure and put it into a data frame, 4. remove the useless data frames
for next loop
> for (j in 1:nrow(ora))
> {
>  ? mycol? <- ora[j,"fname"]
> #--------------------work on csv------------
>  ? mycsv? <- paste0(mycol,".csv")
>  ? rdcsv? <- noquote(paste0("w:/project/_Joe.B/Oracle/data/",
mycsv))
>  ? rr? ? ?<- read.csv(rdcsv)
>
> #--------------------work on SS ------------
>  ? myss? ?<- paste0("gemd.", mycol)
>  ? rdss? ?<- paste0('select * from ',myss)
>  ? ss? ? ?<- dbGetQuery(con, rdss)
>    
> #--------------------compare DF structure? ?------------
> str_rr <- as.data.frame(summary.default(rr))
> str_ss <- as.data.frame(summary.default(ss))
>
>
> sdif_[j] <- sqldf('select * from str_rr except select * from
str_ss')
>
> #---------remove data frame from memory--------------
>
>  ? rm(rr)
>  ? rm(ss)
>  ? rm(str_rr)
>  ? rm(str_ss)
> }
> In the step 3, I want to use ora$fname in the loop to?assign a data frame
name. So, I will look the output later. But?sdif_[j] doesn't work for this.
Can someone help me to fix this part?
> Thanks,
> Kai
> 	[[alternative HTML version deleted]]
>
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