R sqlSave String Variables Loop Issues

Question

I'm just now jumping back in the land of R after a few years away and am running into a problem passing variables through a loop with sqlSave. I've got RODBC up and running smoothly with MySQL on a Win7 box but can't seem to get my loops to work. Here's what data I have and what I'm trying to accomplish:

• MLB Play-by-play data for 2012 using the pitchRX library saved as a single "value" called "mlb12" with multiple tables
• "mlb12" has seven tables inside of it (atbat, pitch, game, player, runner, umpire, coach)
• I want to create a loop that will create a data frame for each of these tables within R so I can then pass them through a loop with sqlSave to insert them into my MySQL database
• I've already inserted all of these tables into my MySQL database but I did it the "long" way (i.e. declaring each DF and creating a sqlSave statement for each insert) and would prefer to do them in two loops to clean up the code.
• Below is the code I currently have to scrape this data and insert it into the MySQL database:

library(RODBC)

library(pitchRx)   

mlb12 <- scrapeFX(start = "2012-04-05", end = "2012-04-07",     
         tables=list(atbat=fields$atbat,pitch=fields$pitch,
         game=fields$game,player=fields$player,
         runner=fields$runner,umpire=fields$umpire,
         coach=fields$coach))

atbat <- mlb12$atbat
pitch <- mlb12$pitch
game <- mlb12$game
player <- mlb12$player
runner <- mlb12$runner
umpire<- mlb12$umpire
coach <- mlb12$coach

channel <- odbcConnect("db", uid = "cs", pwd = "pw")
sqlSave(channel,mlb12$atbat,tablename="atbat")
sqlSave(channel,mlb12$pitch,tablename="pitch")
sqlSave(channel,mlb12$game,tablename="game")
sqlSave(channel,mlb12$player,tablename="player")
sqlSave(channel,mlb12$runner,tablename="runner")
sqlSave(channel,mlb12$umpire,tablename="umpire")
sqlSave(channel,mlb12$coach,tablename="coach")
close(channel)  

The loops that I've tried to write, both to set up the data frames and to simplify the sqlSave statements, both failed to execute properly. Here's an example of one I tried that I thought would have worked:

i<-0
while (i<6) {
i<-i+1
a<-c("atbat","pitch","game","player","runner","umpire","coach")
b<-paste("mlb12$",a,sep="")
c[[i]]<-paste("test",i,sep="")
  }

The problem with this loop is that I can't remember how (or figured out how) to use the c[[i]] incremental field to take the "b" values to create the data frame for each table from the list. I'm fairly certain if I could get this issue resolved I could get a loop to work for the "sqlSave" section. Is there a way to do what I'm trying to do with the autoincremental field (or with a field based on a second list)?

Answer 1

You can use lapply for example like this :

channel <- odbcConnect("db", uid = "cs", pwd = "pw")
a<-c("atbat","pitch","game","player","runner","umpire","coach")
lapply(a,function(x) 
     sqlSave(channel,mlb12[[x]],tablename=x)
close(channel)