Hi Test made in: R in windows Vista OS, R version 2.8.1 From FAQ: http://cran.r-project.org/doc/FAQ/R-FAQ.html#How-do-I-convert-factors-to-numeric_003f "It may happen that when reading numeric data into R (usually, when reading in a file), they come in as factors. If |f| is such a factor object, you can use as.numeric(as.character(f)) to get the numbers back."
1: Why it may happen? Why R transforms x1 from real numeric with decimal values into factor??? 2: Doesn't it look strange to get "internal numbers" when one applies as.numeric(x$x1)? 3. What are the internal numbers mentioned in the FAQ? Why is needed to write: as.numeric(as.character(x$x1)) to get finally the right numbers I read with read.table? Are the missing values shown as dot to force R (or the programmer who wrote the function read.table) to consider x1 as factor? Is it possible who is maintaining the read.table function to improve it to recognize numbers with decimal places as numeric and not as factors and dots as missing values which transform into NA? The data file saved as text: test.txt ob,x1,y1 1,1.1,1/1 2,2.1,1/2 3,3.2,2/2 4,.,0/0 5,4.5,1/1 6,5.1,0/0 7,6.3,1/1 8,.,1/2 reading it from d directory: x<-read.table(file="d:\\test\\test.txt",header=T,sep=',') > x ob x1 y1 1 1 1.1 1/1 2 2 2.1 1/2 3 3 3.2 2/2 4 4 . 0/0 5 5 4.5 1/1 6 6 5.1 0/0 7 7 6.3 1/1 8 8 . 1/2 > as.numeric(x$x1) [1] 2 3 4 1 5 6 7 1 > as.numeric(as.character(x$x1)) [1] 1.1 2.1 3.2 NA 4.5 5.1 6.3 NA Warning message: NAs introduced by coercion Thanks, Aldi [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.