Question

我在R中编写了一个脚本，它将csv文件读取到数据帧，然后操纵该数据帧以创建一个新的数据帧。当前脚本如下：

#read in the csv file for a node
node00D = read.csv("00D.csv")

#create a new data frame with the specific measurement we want to decrease file size
node00D_smaller = node00D[node00D$sensor=="BMP180",]

#remove the columns that we don't need
keeps = c("node_id","timestamp","parameter","value")
node00D = node00D_smaller[keeps]

#fix row names
rownames(node00D) = 1:nrow(node00D)

#convert the timestamp column from a factor to a date and then truncate to the hour
node00D$timestamp = as.POSIXlt(node00D$timestamp)
node00D$timestamp = trunc(node00D$timestamp,"hour")
rm(keeps,node00D_smaller)

#get average temperature for each hour
library(plyr)
node00D$timestamp = as.character(node00D$timestamp)
node00D_means = ddply(node00D, .(timestamp), summarize,
                      mean=round(mean(value),2))
node00D$timestamp = as.POSIXlt(node00D$timestamp)
node00D_means$timestamp = as.POSIXlt(node00D_means$timestamp)
write.csv(node00D_means,"00D_Edit.csv")

#load lat long data
latlong = read.csv("Node.Lat.Lon.csv")
node00D_means$Node = "00D"
node00D_means = merge(node00D_means,latlong,by="Node")

我必须为多达100个节点执行此操作，因此我尝试使用参数'node'编写一个函数来执行此操作。在这个例子中，我将输入getNodeData（00D）。但是，当我这样做时，实际上存在创建数据帧的问题。该函数运行但不创建任何新对象。有没有办法将此脚本转换为函数，以便我可以更轻松地执行100次？

Answer 1

您可以执行类似

的操作

$#some

现在这个函数没有返回任何内容，但它保存了fun1 <- function(node.num){ ### (1). Load the data dat <- read.csv(paste0(node.num, ".csv")) dat_smaller <- dat[dat$sensor=="BMP180",] ### (2). Here proceed with your code and substitute node00D(_smaller) by dat(_smaller) ### # ------------------------------------------------------------------- # ### (3). Then define dat_mean and save the .csv library(plyr) dat$timestamp=as.character(dat$timestamp) dat_means=ddply(dat,.(timestamp),summarize,mean=round(mean(value),2)) dat$timestamp=as.POSIXlt(dat$timestamp) dat_means$timestamp=as.POSIXlt(dat_means$timestamp) write.csv(dat_means,paste0(node.num, "_Edit.csv")) ### (4). And similarly for lat long latlong=read.csv("Node.Lat.Lon.csv") dat_means$Node=node.num dat_means=merge(dat_means,latlong,by="Node") }个文件。但是，如果你想要它返回一些东西，例如.csv，然后您可以在函数结束前添加行dat_means。

<强>附录

现在要动态执行上述操作，您可以使用循环：

return(dat_means)

现在我不知道您的数据，但如果节点包含在### (1.) First, create an object containing all your nodes, e.g. nodes.vector <- c("00D", ...) ### (2.) Run a loop, or use one of the apply functions for(k in seq_along(nodes.vector)){ fun1(nodes.vector[k]) } # Or sapply(nodes.vector, fun1)中，那么您可以将其设置为latlong$Node。

有没有办法在R中编写一个函数来编写像这个脚本中的数据帧？

1 个答案: