R - 循环cbind()结果的累积存储和可能的解决方案,以双重for循环 [英] R - Cumulative storage of looped cbind() results and possible lapply solution to double for-loop
问题描述
我找到了解决方案的一个解决方案问题我发布了基于@ Ryan的建议,由此代码给出:
网页< - read_html(url [i])#loop通过URL列表访问html数据
fac_data < - html_nodes(网页,'。表格')%>%html_text()
fac_data1< - html_nodes(网页,'。表格1')%>%html_text()
fac_data< - c(fac_data,fac_data1)#在变量
x< - fac_data%>%矩阵(ncol = length(headers [[i]))中存储每个URL的表数据,byrow = TRUE )#make矩阵提取列数据
(seq_along(headers [[i]])){
y < - cbind(x [,j])中的j列提取列数据并存储在临时变量
colnames(y)< - as.character(headers #add列名称
print(cbind(y))#loop通过标题列表按顺序打印列数据。 **当我尝试将结果存储在列表中时,cbind(y)将被覆盖,其中'z < - cbind(y)'。
$ b我现在可以打印出所有的值,完成与问题的数据标题。
一些后续问题将是:
如何将cbind(y)的输出累积地保存在data.frame或list中?循环遍历cbind(y)将覆盖值,这使得我只剩下最后一个表的最后一列。像这样:
退休年月
<1>82年8月
这些变化都无效:
z [[x]] [j]< - cbind(y)
> ('〜/ Google云端硬盘/R/scrapeFaculty.R')
在* tmp * [[x]]错误:最多只能选择一个元素
z [j] < - cbind(y)
> source('〜/ Google云端硬盘/R/scrapeFaculty.R')
有13条警告(使用warnings()来查看)
z [[j]]< - cbind (y)
> source('〜/ Google云端硬盘/R/scrapeFaculty.R')
z [[j]]中的错误< - cbind(y):用来替换的元素比所要替换的值多
- 可以用简单的lapply替换double for-loop ()函数为
解决上述问题?
$ b编辑:
这是我用来解决这个问题的最终代码:
$ b $ pre $for(i in seq_along(url)){
网页< - read_html(url [i])
fac_data< - html_nodes(网页,'。tableunder')%>%html_text()
fac_data1< ; html_nodes(webpage,'。tableunder1')%>%html_text()
fac_data <-c(fac_data,fac_data1)
x< - fac_data%>%矩阵ncol = length(headers [[i]]),byrow = TRUE)#make矩阵提取列数据
y < - cbind(x [,1:length(headers [[i]])])#extract列数据
colnames(y)< - as.character(headers [[i]])#add colunm name
ntu.hist [[i]]< - y #Cumul在列表上吃了结果。
解决方案想知道这是否是一个选项,而不是循环一次cbind多个。这些语法选项是否有帮助?
y < - data.frame(col1 = c(1:3),col2 = c(4:6),col3 = c(7:9))
cbind(y [,c(1:3)])
col1 col2 col3
1 1 4 7
2 2 5 8
3 3 6 9
#在R中,可以用:指定一个范围。所以1,2,3,4等于1:4。
#如果你不想要那个范围内的数字3,你可以使用c(1,2,4)。
例如:
cbind(y [,c(1,3)])
col1 col3
1 1 7
2 2 8
3 3 9
I've found a work around solution to a question I posted based on @Ryan's recommendation, given by this code:
for (i in seq_along(url)){ webpage <- read_html(url[i]) #loop through URL list to access html data fac_data <- html_nodes(webpage,'.tableunder') %>% html_text() fac_data1 <- html_nodes(webpage,'.tableunder1') %>% html_text() fac_data <- c(fac_data, fac_data1) #Store table data on each URL in a variable x <- fac_data %>% matrix(ncol = length(headers[[i]]), byrow=TRUE) #make matrix to extract column data for (j in seq_along(headers[[i]])){ y <- cbind(x[,j]) #extract column data and store in temporary variable colnames(y) <- as.character(headers[[i]][j]) #add column name print(cbind(y)) #loop through headers list to print column data in sequence. ** cbind(y) will be overwritten when I try to store the result on a list with 'z <- cbind(y)'. } }
I am now able to print out all values, complete with headers of the data in question.
Some follow-up questions will be:
How do I save the output of cbind(y) cumulatively in a data.frame or a list? Looping through cbind(y) will overwrite values, which leaves me with only the last column from the last table. Like this:
退休年月
[1,] "82年8月"
Neither do these variations work:
z[[x]][j] <- cbind(y) > source('~/Google 云端硬盘/R/scrapeFaculty.R') Error in `*tmp*`[[x]] : 最多只能選擇一個元素 z[j] <- cbind(y) > source('~/Google 云端硬盘/R/scrapeFaculty.R') There were 13 warnings (use warnings() to see them) z[[j]] <- cbind(y) > source('~/Google 云端硬盘/R/scrapeFaculty.R') Error in z[[j]] <- cbind(y) : 用來替換的元素比所要替換的值多
- Can the double for-loop be replaced by a simple lapply() function to resolve the above issue?
EDIT:
Here's the final code I used to solve this:
for (i in seq_along(url)){ webpage <- read_html(url[i]) fac_data <- html_nodes(webpage,'.tableunder') %>% html_text() fac_data1 <- html_nodes(webpage,'.tableunder1') %>% html_text() fac_data <- c(fac_data, fac_data1) x <- fac_data %>% matrix(ncol = length(headers[[i]]), byrow=TRUE) #make matrix to extract column data y <- cbind(x[,1:length(headers[[i]])]) #extract column data colnames(y)<- as.character(headers[[i]]) #add colunm name ntu.hist[[i]] <- y #Cumulate results on a list. }
解决方案I was wondering if it would be an option to cbind multiple at one time instead of looping. Would any of these syntax options help?
y <– data.frame(col1=c(1:3),col2=c(4:6),col3=c(7:9)) cbind(y[,c(1:3)]) col1 col2 col3 1 1 4 7 2 2 5 8 3 3 6 9 #In R, you can use ":" to specify a range. So 1,2,3,4 is equal to 1:4. #If you don't want number 3 in that range, you can use c(1,2,4). #For example: cbind(y[,c(1,3)]) col1 col3 1 1 7 2 2 8 3 3 9
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