從R中的data.frame創建新的類

Question

我在R中使用函數，類和方法。 要進行「手動」練習也可能有用，我決定創建我的「包」照顧我的家庭預算。 簡而言之，我想要一系列函數，類和方法來計算東西，繪製不同類型的圖表，哪些不是。 我想要做的第一件事就是創建一個「Budget」類：它應該帶有某些列的csv，並返回一個對象「Budget」，它繼承了數據框的相同方法，但是我可以將其應用於一組「預算」方法。 這是我拿

prepareData = function (csv, type=1) { 

if (type == 1) { 
Data = read.csv(csv,dec = ".")} 
else if (type == 2) { 
Data = read.csv2(csv,dec = ",")} 
else {stop ("Accetable value for type are 1 and 2")} 

NamesToHave = c("Date","Title","Amount","Category") 

if (sum(as.numeric(colnames(Data) %in% NamesToHave)) < 4) { 
    stop ("The csv file has not the mandatory columns (Data, Title, Amount, Category)")} 




if (class(try(tolower(Data$Title),silent = T)) == "try-error" | class(try(tolower(Data$Category),silent = T)) == "try-error") { 
    stop("Are you sure there are no special character in your csv file ?")} 

Data$Day = sapply(strsplit(as.character(Data$Date), "/"),"[[",1) 
Data$Month = month.abb[as.numeric(sapply(strsplit(as.character(Data$Date), "/"),"[[",2))] 
Data$Year = sapply(strsplit(as.character(Data$Date), "/"),"[[",3) 

Data = Data[with(Data, order(Year, Month, Day)), ] 
Data$Amount = as.character(Data$Amount) 
Data$Amount = as.numeric(as.character(Data$Amount)) 

class(Data) <- append(class(Data),"Budget") 
return(Data) 
} 

現在，這個返回一個數據幀的所有必要的修改，並且總體而言，它正常工作的功能，但如果我把一個csv如下

structure(list(Date = structure(c(22L, 1L, 1L, 1L, 1L, 1L), .Label = c("01/10/2016", 
"01/11/2016", "02/10/2016", "04/10/2016", "04/11/2016", "05/10/2016", 
"05/11/2016", "06/10/2016", "06/11/2016", "07/10/2016", "08/10/2016", 
"08/11/2016", "09/10/2016", "09/11/2016", "10/10/2016", "10/11/2016", 
"11/10/2016", "12/11/2016", "14/10/2016", "16/10/2016", "18/10/2016", 
"20/09/2016", "20/10/2016", "21/10/2016", "22/09/2016", "22/10/2016", 
"23/09/2016", "23/10/2016", "25/09/2016", "25/10/2016", "26/09/2016", 
"26/10/2016", "27/10/2016", "28/10/2016", "29/10/2016", "30/10/2016" 
), class = "factor"), Title = structure(c(20L, 6L, 36L, 29L, 
30L, 11L), .Label = c("Bagpiper", "beer debaser", "Br", "brewdog", 
"Burger King", "Clas", "coop", "Coop", "Eriksdalbadet", "etc", 
"ETC", "Flippin", "Fotografiska", "Gateau Agneta", "Grekisk fastfood", 
"Grill", "Gunnarson", "Gunnarsson", "hemkop", "HK", "Hotorhallen", 
"ICA", "ICA Skinnskat", "Igor Sport", "Intersport", "Kak", "klattercentret", 
"LullesFagel", "Mae Thai", "MamaWolf", "Material", "Matrerial", 
"Oriental Supermarket", "Paradiset", "Pendeltag Uppsala", "PGW", 
"Pressbyran", "Primeburger", "Primo Ciao ciao", "R Asia", "Systembolaget", 
"taxi Skinnskat", "The Cure drinks", "Udden pensionat", "Ugglan", 
"Wentzels hobby"), class = "factor"), Amount = c(167.27, 331, 
971, 99, 192, 3289), Category = structure(c(10L, 3L, 3L, 6L, 
6L, 3L), .Label = c("Drink", "extra", "Extra", "Extra_Fede", 
"extra_food", "Extra_food", "extra_laure", "Extra_Laure", "food", 
"Food"), class = "factor")), .Names = c("Date", "Title", "Amount", 
"Category"), row.names = c(NA, 6L), class = "data.frame") 

和我跑

Data = prepareData("name.csv") 
class(Data) 

輸出只是「data.frame」。但是，如果我然後從終端再次運行功能的倒數第二行

class(Data) <- append(class(Data),"Budget") 
class(Data) 

我得到了「data.frame」和「預算」作爲輸出。

我在做什麼錯？

Answer 1

你的問題在這裏：

if (as.numeric(colnames(Data) %in% NamesToHave) != 4) {} 

第一比較 - 將矢量執行和返回TRUE TRUE TRUE TRUE，走的時候扔as.numeric()這將成爲1 1 1 1。然後，這個向量將被比較爲!= 4，這是矢量化執行並返回TRUE TRUE TRUE TRUE（所有的'不同於四'）。 if（）`語句不會評估整個向量，只是它的第一個元素（並且會引發一條警告消息）。

要解決此問題，您只需將as.numeric()函數切換爲sum()。

if (sum(colnames(Data) %in% NamesToHave) != 4) {} 

當你總結的邏輯向量，R將它強制給數值：所有TRUE成爲1和所有FASLE成爲0。現在，您將擁有4條將在if語句中評估FALSE的總和以及它運行平穩的功能。一旦我解決了它，當我第一次運行它時，它就有兩個類。

正如this article所述，在發佈您的問題之前重新啓動R並確保您仍然存在您要報告的問題。