[英]Loop through url's with R
I need to download a series of Excel files from URL's that all look as follows: 我需要从URL下载一系列Excel文件,如下所示:
http://example.com/orResultsED.cfm?MODE=exED&ED=01&EventId=31
http://example.com/orResultsED.cfm?MODE=exED&ED=02&EventId=31
...
http://example.com/orResultsED.cfm?MODE=exED&ED=87&EventId=31
I've got some of the building blocks inside the loop, such as: 我在循环中有一些构建基块,例如:
for(i in 1:87) {
url <- paste0("http://example.com/orResultsED.cfm?MODE=exED&ED=", i, "&EventId=31")
file <- paste0("Data/myExcel_", i, ".xlsx")
if (!file.exists(file)) download.file(url, file)
}
My problems : 我的问题 :
seq
to prepend the 0 (I tried sprintf
with no luck) seq
放在0之前(我没有运气就尝试了sprintf
) @akrun solution works well. @akrun解决方案效果很好。 But it turns out not all my Excel files have the same number of columns:
但事实证明,并非我所有的Excel文件都具有相同的列数:
map(files, ~read.xlsx(.x,
colNames = FALSE,
sheet = 1,
startRow = 4,
)) %>%
bind_rows
Error in bind_rows_(x, .id) :
Column `X1` can't be converted from numeric to character
I think this error actually points to the unequal number of column. 我认为此错误实际上指向不相等的列数。 I tried adding
fill = NA
(when testing map_df()
), but it didn't help. 我尝试添加
fill = NA
(在测试map_df()
),但没有帮助。
We can create it with sprintf
我们可以用
sprintf
创建它
paste0("http://example.com/orResultsED.cfm?MODE=exED&ED=", sprintf("%02d", 1), "&EventId=31")
#[1] "http://example.com/orResultsED.cfm?MODE=exED&ED=01&EventId=31"
In the loop, 在循环,
for(i in 1:87) {
i1 <- sprintf('%02d', i)
url <- paste0("http://example.com/orResultsED.cfm?MODE=exED&ED=", i1, "&EventId=31")
file <- paste0("Data/myExcel_", i, ".xlsx")
if (!file.exists(file)) download.file(url, file)
}
Assuming that the files are downloaded in the working directory 假设文件已下载到工作目录中
files <- list.files(full.names = TRUE)
library(openxlsx)
library(purrr)
library(dplyr)
map(files, ~read.xlsx(.x, sheet = 1, startRow = 3)) %>%
bind_rows
Or as @hrbrmstr mentioned in the comments, map_df
can be used which returns a single dataset 或如评论中提到的
map_df
可以使用map_df
返回单个数据集
map_df(files, ~read.xlsx(.x, sheet = 1, startRow = 3))
Based on the comments from OP, there seems to be a difference in column class for some of the datasets. 根据OP的评论,某些数据集的列类似乎有所不同。 In that case,
bind_rows
gives an error. 在这种情况下,
bind_rows
会给出错误。 One option is to use rbindlist
from data.table
一种选择是使用
rbindlist
的data.table
map(files, ~read.xlsx(.x, sheet = 1, startRow = 3)) %>%
data.table::rbindlist(fill = TRUE)
downloading and reading in 1 loop. 1次循环下载和阅读。 Hopefully, the columns are aligned if not use something like
plyr::rbind.fill
instead of do.call(rbind, list)
希望如果不使用
plyr::rbind.fill
而不是do.call(rbind, list)
类的话,列是对齐的
do.call(rbind, lapply(1:87, function(n) {
url <- paste0("http://example.com/orResultsED.cfm?MODE=exED&ED=",
sprintf("%02d", n), "&EventId=31")
file <- paste0("Data/myExcel_", n, ".xlsx")
if (!file.exists(file)) download.file(url, file)
readxl::read_excel(file, skip=2)
Sys.sleep(5)
}))
you can also use regmatches
您还可以使用
regmatches
num=sprintf("%02.0f",1:87)
urls=rep("http://example.com/orResultsED.cfm?MODE=exED&ED=01&EventId=31",87)
`regmatches`(urls,regexpr("\\d+",urls))<-num
urls[87]
[1] "http://example.com/orResultsED.cfm?MODE=exED&ED=87&EventId=31"
To have all the files: 要拥有所有文件:
files <- paste0("Data/myExcel_",num , ".xlsx")
to download the files: 下载文件:
mapply(function(x,y)if(!file.exists(x))download.file(y,x),files,urls)
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