plot with ggplot in for-loop doesn't work [duplicate]

Answer 1

For starters, it looks like you're always picking the "A" subset. The beginning of the for loop should look like:

for(i in sp){
 table <- data[data$sp==i,]

Answer 2

using print() is required with qplot() as well in for loop

e.g. I had the following format of code but only blank image files were created when using qplot()

for(loop1 in rangestart:rangeend)  
{  
   ..........  
   ..........  
   png(Imagefile,width=1366,height=768)  
   qplot(.....)  
   dev.off()  
}

Replacing qplot(.....) with print(qplot(.....)) solved the problem

Answer 3

The problem is the for loop. You need to use print in a loop.

for (i in sp) {
  table <- data[data$sp=="A",]
  windows()
  ggp <- ggplot(...) + ...
  print(ggp)
}

Consider this simple example:

library(ggplot2)
df=data.frame(x=1:10,y=rnorm(10))                       # sample data
ggplot(df)+geom_point(aes(x,y))                         # render ggplot
for (i in 1:2) ggplot(df)+geom_point(aes(x,y))          # nothing
for (i in 1:2) print(ggplot(df) + geom_point(aes(x,y))) # renders

Also, as @user229552 says, you are using the same table both times.