从多个文件作为两列矩阵的操作中获得结果

Question

I'm using a for-loop to loop through files in a directory. Then I do a set of processing on the data in each file and write a matrix with 10 rows. This is my code.

for(i in 1:length(testData))
      {
        MAE[1,i] = abs(forecastData$mean[i] - testData[i])
      }

Now I wish to wish to do the following:

• add the rows in this matrix
• write it as a value in a separate two column matrix with the filename being the first column and the value as the second column
• sort it as per the value(not filename)
• access it globally(ie, outside the for loop that iterates through the directory).

The number of rows for this matrix will be the total number of files in the directory(dynamically assigned is what I mean). How can I achieve this functionality?

Answer 1

It is difficult to give a comprehensive answer because there is no example. In general, however, I would use list.files() to obtain a vector of all the files in question, and then write a function that performed whatever math you need done on each file. Such a function could look something like this.

func.file_math <- function(file.name) {

    <insert file operations>
    return(list(file.name=file.name,
                number=number))
}

Using sapply() you could then run this over all the contents of your file.list() . Once done, you can simply use do.call() and rbind.data.frame to get a data frame of the results.

yourfiles <- list.files("/some/path/")
file_math <- sapply(X=yourfiles,
                    FUN=func.file_math,
                    simplify=FALSE,
                    USE.NAMES=TRUE)
file_math.df <- do.call(what=rbind.data.frame,
                        args=file_math)