在 R 中手动计算方差 [英] Calculate Variance Manually in R

问题描述

我需要你的帮助.我需要在 R 中手动计算方差.我已经用这个代码实现了它，它对于缺失值和非数字数据类型不够健壮.

I need your help here. I need to calculate variance manually in R. I have achieved it with this codes, it is to not robust enough for missing values and non-numeric data types.

a= c(1,2,3,4,5)
k=mean(a,na.rm = T)
storage=a
for(i in 1:length(a)) {
  storage[i]= ((i-k)^2)
}
storage =sum((storage)/(length(a)-1))
storage

当我有 a= c(1,2,3,4,5,c,NA) 时，我遇到了麻烦请问我将如何编辑代码?

I run into trouble when I have a= c(1,2,3,4,5,c,NA) Please how would I edit the code?

推荐答案

您正在使用 for 循环，但这确实是不必要的，您可以创建一个函数对其进行矢量化，作为第一步，通过转换为字符然后是数字向量类型(因为 c 是一个函数)...

You are using a for loop but that is really unnecessary, you can make a function to vectorise it which removes the NAs from the data as the first step, via conversion to character then numeric vector types (because c is a function)...

# Create data
set.seed(1)
x1 <- sample(1:10, 5)
x2 <- c(x1, c, NA)

# Make the function
varFunc <- function(x){
 # Convert to character then numeric (non numeric become NA) then remove NAs
  x <- as.numeric(as.character(x))[!is.na(as.numeric(as.character(x)))]
  # Return Variance 
  sum((x-mean(x))^2) / (length(x)-1)
}

# Use the function 
varFunc(x1)
varFunc(x2)

# Sanity check
var(x1)
var(x2, na.rm = TRUE)

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