如何為每一行應用公式

Question

我有這樣的數據

df<-structure(list(data = structure(c(8L, 2L, 3L, 2L, 2L, 2L, 2L, 
1L, 7L, 5L, 6L, 5L, 4L), .Label = c("1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0", 
"2, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0", 
"2, 2, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0", 
"2, 2, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0", 
"2, 2, 2, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0", 
"3, 2, 2, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0", 
"M1yrtr", "Mitered"), class = "factor")), row.names = c(NA, -13L), class = "data.frame")

我正在嘗試為每一行計算以下內容

例如第二行

2, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

我要計算這個

n =5
(-(2/n)*log2(2/n)) + (-(1/n)*log2(1/n)) +(-(1/n)*log2(1/n))+ (-(1/n)*log2(1/n)) 

對於第三個是

2, 2, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

我會計算一下

(-(2/n)*log2(2/n)) + (-(2/n)*log2(2/n)) + (-(1/n)*log2(1/n))

所以輸出看起來像這樣

dfout<- structure(list(data = structure(c(8L, 2L, 3L, 2L, 2L, 2L, 2L, 
1L, 7L, 5L, 6L, 5L, 4L), .Label = c("1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0", 
"2, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0", 
"2, 2, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0", 
"2, 2, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0", 
"2, 2, 2, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0", 
"3, 2, 2, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0", 
"M1yrtr", "Mitered"), class = "factor"), X = structure(c(8L, 
3L, 2L, 3L, 3L, 3L, 3L, 1L, 7L, 6L, 4L, 6L, 5L), .Label = c("0.2604594", 
"1.03563", "1.168964", "2.020935", "2.077468", "2.204594", "M1yrtr", 
"Mitered"), class = "factor")), class = "data.frame", row.names = c(NA, 
-13L))

Answer 1

在R中，所有基本運算（加減，乘法，對數等）都被矢量化。 這意味着，例如，如果x是向量，則log(x)只是按分量log函數，而礦石1 / x只是按分量對數的除法。

因此，您可以執行以下操作：

x <- as.numeric(str_split(df[2, ], ", ", simplify = T))
n <- 5
sum((-(x[x > 0]/n)*log2(x[x > 0]/n)))
[1] 1.921928

如果要將其應用於所有行，則可以使用sapply函數，如下所示：

myfun <- function(x){
 if (! grepl(",", x)) return(as.character(x))
  n <- 5
  y <- as.numeric(str_split(x, ", ", simplify = T))
  as.character(sum((-(y[y > 0]/n)*log2(y[y > 0]/n))))
}

df$newcol <- sapply(df[,1], myfun)