如何使R函數返回多個列並將它們附加到數據框？

這個數據幀開始如何使R函數返回多個列並將它們附加到數據框？

myDF = structure(list(Value = c(-2, -1, 0, 1, 2)), .Names = "Value", row.names = c(NA, 5L), class = "data.frame")

假設我要上運行的是myDF $價值

getNumberInfo <- function(x) { 
if(x %% 2 ==0) evenness = "Even" else evenness="Odd" 
if(x > 0) positivity = "Positive" else positivity = "NonPositive" 
if (positivity == "Positive") logX = log(x) else logX=NA 
c(evenness,positivity,logX) 
}

...每一行這個函數來得到這個數據幀

structure(list(Value = c(-2, -1, 0, 1, 2), Evenness = c("Even", 
"Odd", "Even", "Odd", "Even"), Positivity = c("NonPositive", 
"NonPositive", "NonPositive", "Positive", "Positive"), Log = c(NA, 
NA, NA, "0", "0.693147180559945")), row.names = c(NA, 5L), .Names = c("Value", 
"Evenness", "Positivity", "Log"), class = "data.frame")

來源

2009-09-08 Dan Goldstein

你可能想要更改getNumberInfo函數返回一個列表而不是一個向量，以便這些值可以有不同的類型。事實上，他們都被投入絃樂，這可能不是你想要的logX。

getNumberInfo <- function(x) { 
    if(x %% 2 ==0) evenness = "Even" else evenness="Odd" 
    if(x > 0) positivity = "Positive" else positivity = "NonPositive" 
    if (positivity == "Positive") logX = log(x) else logX=NA 
    list(evenness,positivity,logX) 
}

此外，還可以使用名稱稍微較好的效果，這樣你就不必贅述：

getNumberInfo <- function(x) { 
    list(evenness = if(x %% 2 ==0) "Even" else "Odd", 
     positivity = if(x > 0) "Positive" else "NonPositive", 
     logX = if(x > 0) log(x) else NA) 
}

然後將溶液變得簡單：

> cbind(myDF, t(sapply(myDF$Value, getNumberInfo))) 
    Value evenness positivity  logX 
1 -2  Even NonPositive  NA 
2 -1  Odd NonPositive  NA 
3  0  Even NonPositive  NA 
4  1  Odd Positive   0 
5  2  Even Positive 0.6931472

最後，如果您使用ifelse（它可以在矢量上工作）而不是if，則它變得更簡單，因爲您無需致電apply：

getNumberInfo <- function(x) { 
    list(evenness = ifelse(x %% 2 ==0, "Even", "Odd"), 
     positivity = ifelse(x > 0, "Positive", "NonPositive"), 
     logX = ifelse(x > 0, log(x), NA)) 
} 

> cbind(myDF, getNumberInfo(myDF$Value)) 
    Value evenness positivity  logX 
1 -2  Even NonPositive  NA 
2 -1  Odd NonPositive  NA 
3  0  Even NonPositive  NA 
4  1  Odd Positive 0.0000000 
5  2  Even Positive 0.6931472

最後的解決方案會發出警告，因爲它實際上是計算每個元素的日誌，而不僅僅是那些使用x>0的日誌。不知道最優雅的方式來處理。

來源

2009-09-08 19:00:13

't（sapply'do）與'tapply'相反嗎？我不知道用't（）'包裝什麼東西，我從來沒有見過它。 – 2016-10-09 00:11:58

如何：

out <- cbind(myDF, t(apply(myDF, 1, getNumberInfo))) 
colnames(out) <- c('Value', 'Evenness', 'Positivity', 'Log')

它給你：

 
    Value Evenness Positivity    Log 
1 -2  Even NonPositive    NA 
2 -1  Odd NonPositive    NA 
3  0  Even NonPositive    NA 
4  1  Odd Positive     0 
5  2  Even Positive 0.693147180559945

來源

2009-09-08 17:38:51

是什麼'噸（apply'do而不是僅僅'tapply'我不知道是什麼東西包裝用'噸（）'不，我從來沒有見過？它記錄下來。 – 2016-10-09 00:11:30

另一種選擇：

> library(plyr) 
> df <- mdply(myDF, getNumberInfo) 
> names(df) <- c('Value', 'Evenness', 'Positivity', 'Log') 
> df 
    Value Evenness Positivity  Log 
1 -2  Even NonPositive  NA 
2 -1  Odd NonPositive  NA 
3  0  Even NonPositive  NA 
4  1  Odd Positive 0.0000000 
5  2  Even Positive 0.6931472

來源

2009-09-09 20:47:10 learnr

如何使R函數返回多個列並將它們附加到數據框？

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