问题描述
我正在学习 R 教程,并怀疑我必须使用其中一个函数,但我不确定是哪个(是的,我研究了它们,但直到我对 R 术语变得更加流利时,它们才变得非常混乱).
I'm working through an R tutorial and suspect that I have to use one of these functions but I'm not sure which (Yes I researched them but until I become more fluent in R terminology they are quite confusing).
在我的工作目录中有一个文件夹specdata".Specdata 包含数百个名为 001.csv - 300.csv 的 CSV 文件.
In my working directory there is a folder "specdata". Specdata contains hundreds of CSV files named 001.csv - 300.csv.
我正在处理的函数必须计算输入的 csv 文件数量的总行数.因此,如果函数中的参数是 1:10
并且每个文件都有 10 行,则返回 100.
The function I am working on must count the total number of rows for an inputed number of csv files. So if the argument in the function is 1:10
and each of those files has ten rows, return 100.
这是我目前所拥有的:
complete <- function(directory,id = 1:332) {
setpath <- paste("/Users/gcameron/Desktop",directory,sep="/")
setwd(setpath)
csvfile <- sprintf("%03d.csv", id)
file <- read.csv(csvfile)
nrow(file)
}
这在 ID 参数是一个数字时有效,比如 17.但是,如果我输入 10:50 作为参数,我会收到一个错误:
This works when the ID argument is one number, say 17. But, if I input say 10:50 as an argument, I receive an error:
Error in file(file, "rt") : invalid 'description' argument
我应该怎么做才能从输入的 ID 参数中计算出总行数?
What should I do to be able to count the total number of rows from the inputed ID parameter?
推荐答案
read.csv
期望只读取一个文件,因此您需要遍历文件,R 惯用的方法是使用 sapply
:
read.csv
expects to read just one file, so you need to loop over files, a R idiomatic way of doing so is to use sapply
:
nrows <- sapply( csvfile, function(f) nrow(read.csv(f)) )
sum(nrows)
例如,这是对您的 complete
函数的重写:
For example, here is a rewrite of your complete
function:
complete <- function(directory,id = 1:332) {
csvfiles <- sprintf("/Users/gcameron/Desktop/%s/%03d.csv", directory, id)
nrows <- sapply( csvfiles, function(f) nrow(read.csv(f)) )
sum(nrows)
}
这篇关于计算一系列csv文件的行数的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!