[R] how to read this kind of csv in R？

[Duncan Murdoch]

On 06/10/2019 7:29 a.m., vod vos via R-help wrote:
> I got hundreds of csv files. The real formats in each csv file are as follows:
> 
> aa(cm)
> 1, 2 , 3,
> 
> bb(mm)
> 1, 2, 3,
> 4, 5, 6,
> 7, 8, 9,
> 
> cc(mm)
> 3, 4, 5,
> 7, 5, 9,
> 6, 5, 8,
> 
> How can I use read.table or read.csv to convert the csv files
> to a tidy data frame format as follow:
> 
> aa, bb, cc
> 1, 1, 3
> 1, 2, 4
> 1, 3, 5
> 2, 4, 7
> 2, 5, 5
> 2, 6, 9
> 3, 7, 6
> 3, 8, 5
> 3, 9, 8
> 
> many thanks.

You'll need more than those two functions to do the transformation you 
want.  To work out what you need, write out the process in detail in 
English (or another natural language), not in code.  For example:

1.  Read aa from file 1.
2.  Read bb from file 2.
3.  Read cc from file 3.
4.  Expand all vectors to the same length.
5.  Combine them into a single dataframe.

Then work out each step separately.  I think you'll want to use 
something like scan("filename", skip = 1, sep = ",") in steps 1, 2, and 
3, but this will add NA values at the end of each line because of the 
final comma, so you could do this:

aa <- scan("file1", skip = 1, sep = ",")
aa <- aa[!is.na(aa)]

and similarly for the others.

I don't know the rules for expanding that you'll need in your real data, 
but for your example step 4 could be

   aa <- rep(aa, each = 3)

Then step 5 could be

   result <- data.frame(aa, bb, cc)

Duncan Murdoch