I have a data and from that, I want to generate boxplot. My file is saved in \"1.txt\" file and it seems like this
R S1G1 S1G2 S2G1 S2G2
1 0.98 0.9
Your comments are a little tough to decipher, but I'm guessing that maybe you wanted a boxplot for each column S1G1, etc. In that case I'd melt your data:
xx <- read.table(textConnection("R S1G1 S1G2 S2G1 S2G2
1 0.98 0.98 0.96 0.89
2 0.89 0.89 0.98 0.88
3 0.88 0.99 0.89 0.87"),header = TRUE, sep ="")
xx1 <- melt(xx, id.vars = "R")
and then you can make side-by-side boxplots using any of the popular graphing idioms:
ggplot(xx1, aes(x = variable, y = value)) +
geom_boxplot()

Or you can use base graphics or lattice (plots omitted):
boxplot(value~variable, data = xx1)
bwplot(value~variable,data = xx1)