[R] Looping multiple output values to dataframe

[David Winsemius]

?list files

... in particular the pattern argument

--  
David Winsemius
On Feb 12, 2009, at 3:38 PM, Stropharia wrote:

>
> Thanks a lot Levi. Your code was much shorter and more elegant. With  
> a few
> minor alterations I got this (see below) to work.
>
> Does anyone know if there is a way to automate getting only the csv
> filenames in a folder (rather than the whole file path)? Or to  
> automate
> extracting the file names from the file paths, once they have been  
> extracted
> using Sys-glob? Thanks.
>
> Steve
>
> # ----------------------------------------START
> R-CODE-----------------------------------
> filenames <- Sys.glob("/Users/Desktop/Test/*.csv")  # get names of  
> files to
> process # use * to get all
>
> variables <- data.frame(1:length(filenames)) # preallocate assuming  
> multiple
> values from each file # creates a dataframe with the same length of  
> rows as
> the number of .csv files to process
>
> docalc <- function(filenames){
>    input <- read.csv(filenames, header=TRUE, na.strings="NA")
>    attach(input)
>    result.A <- x[2]*y[1]
>    result.B <- y[2]-x[1]
>    result.C <- x[3]+y[1]
>    results <- c(result.A, result.B, result.C) # concatenate result  
> vectors
>    names(results) <- c("ResultA", "ResultB", "ResultC") # set names  
> for
> result vectors
>    return(results)
> }
>
> variables <- t(sapply(filenames, docalc)) # transpose and sapply  
> filenames
>
> # export to csv file
> write.csv(variables, file="/Users/Desktop/Test.csv")
> # ----------------------------------------END
> R-CODE-----------------------------------
>
>
>
>
>
>
> Levi Waldron-3 wrote:
>>
>> Stropharia wrote:
>>> # ----------------------------------------START
>>> R-CODE-----------------------------------
>>> filenames <- Sys.glob("/Users/Desktop/Test/*.csv")  # get names of  
>>> files
>>> to
>>> process # use * to get all
>>>
>>> variables <- data.frame(1:length(filenames)) # preallocate assuming
>>> multiple
>>> values from each file # creates a dataframe with the same length  
>>> of rows
>>> as
>>> the number of .csv files to process
>>>
>>> for (i in seq_along(filenames)){
>>>    input <- read.csv(filenames[i], header=TRUE, na.strings="NA")
>>>    data.frame("input")
>>> 	attach(input)
>>> 	
>>> result.A <- x[2]*y[1]
>>> result.B <- y[2]-x[1]
>>> result.C <- x[3]+y[1]
>>>
>>> results <- c(result.A, result.B, result.C) # concatenate result  
>>> vectors
>>>
>>> variables[i] <- results
>>> }
>>>
>>> variables <- as.data.frame(t(as.matrix(variables))) # turn result  
>>> vectors
>>> into a matrix, then transpose it and output as a data frame
>>>
>>> # add column and row names
>>> c.names <- c("ResultA", "ResultB", "ResultC") # set names for result
>>> vectors
>>> colnames(variables) <- c.names
>>> rownames(variables) <- filenames
>>>
>>> # export to csv file
>>> write.csv(variables, file="/Users/Desktop/Test.csv")
>>> # ----------------------------------------END
>>> R-CODE-----------------------------------
>>>
>> I think something like this should work better:
>>
>> docalc <- function(thisfile){
>>    input <- read.csv(filenames[i], header=TRUE, na.strings="NA")
>>    attach(input)
>>    result.A <- x[2]*y[1]
>>    result.B <- y[2]-x[1]
>>    result.C <- x[3]+y[1]
>>    results <- c(result.A, result.B, result.C) # concatenate result
>> vectors
>>    names(results) <- c("ResultA", "ResultB", "ResultC")
>> return(results)
>> }
>>
>> variables <- sapply(filenames,docalc)
>>
>> -- 
>> Levi Waldron
>> post-doctoral fellow
>> Jurisica Lab, Ontario Cancer Institute
>> Division of Signaling Biology
>> IBM Life Sciences Discovery Centre
>> TMDT 9-304D
>> 101 College Street
>> Toronto, Ontario M5G 1L7
>> (416)581-7453
>>
>> ______________________________________________
>> R-help at 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.
>>
>>
>
> -- 
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>
> ______________________________________________
> R-help at 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.