[R] R is converting arg input to scientific notation, which is bad!

[David Winsemius]

On Jun 19, 2014, at 12:08 PM, efridge wrote:

> Hello,
> 
> Firstly, real new to R here.
> 
> I have a function intended to evaluate the values in columns spread over
> many tables. I have an argument in the function that allows the user to
> input what sequence of tables they want to draw data from. The function
> seems to work fine, but when the user inputs a single number (over 9)
> instead of a sequence using the : operator, I find an error message:
> 
> the input for this example is 30
> 
> Error in file(file, "rt") : cannot open the connection
> 
> 5 file(file, "rt")
> 
> 4 read.table(file = file, header = header, sep = sep, quote = quote, dec =
> dec, fill = fill, comment.char = comment.char, ...)
> 
> 3 FUN("specdata/3e+01.csv"[[1L]], ...)
> 
> 2 lapply(filepaths, read.csv)
> 
> 1 pollutantmean("specdata", "nitrate", 30)
> 
> In addition: Warning message:
> 
> In file(file, "rt") : cannot open file 'specdata/3e+01.csv': No such file or
> directory
> 
> *The problem is that when a single number (30, 104, 223) is input, it's
> being stored as 3e+01 and no longer corresponds with the .csv file I'm
> trying to call (030.csv).*
> 
> Below is my code:
> 
> pollutantmean <- function(directory, pollutant, id = 1:332){
> filenames <- paste0(formatC(id, digits = 0, width = 3, flag = "0"), ".csv")
> filepaths <- file.path(directory, filenames)
> list_of_data_frames <- lapply(filepaths, read.csv)
> big.df<-do.call(rbind,list_of_data_frames)
> print(str(big.df))
> mean(big.df[,pollutant], na.rm=TRUE)
> }
> 
> I'm curious if formatC() is converting the number to scientific notation or
> is that the default for R if there is no sequence when there could be.

I think it's your `digits = 0` argument:

> formatC(20, digits = 3, width = 3, flag = "0")
[1] "020"


> 
> Many of you probably recognize this as a coursera assignment. It's beyond
> the due date and I've submitted some (pretty not good) code for it. I just
> want to have a good understanding of what's going on here, as this type of
> work is directly related to my research.
> 
> 

-- 

David Winsemius
Alameda, CA, USA