如何使用 for 循环对多个变量运行配对 wilcoxon 测试

Question

我正在尝试使用 for 循环对多个变量运行配对 Wilcoxon 测试。但是，它给了我关于公式（x~y）的错误。我尝试了不同的方法来定义 x、y，但没有成功。

我附上了数据的子集和带有错误消息的代码。

Visit       Var1     Var2    Var3
BSL                 24.378  23.045
BSL         9.602   10.08   21.624
BSL         9.01    0       10.858
BSL        4.524    17.86   9
BSL         3.75    8.656   22.575
BSL                         15.83
BSL        6.596    5.34    16.956
BSL        7.065    17.801  16.505
BSL        6.877    3.408   
BSL       15.651            31.983
LV                 18.226   21.009
LV         2.225    6.605   14.191
LV         7.417    15.61   
LV          1.42             1.392
LV                 15.965   22.149
LV                           6.701
LV         2.752    24.364  
LV         6.504    7.371   27.116
LV         7.594    14.391  13.875
LV         6.652            21.985



# 1st test
for (i in (2:ncol(Data_pairs))) {  
        group <- Data_pairs[,1]
        
         result <- wilcox_test(data=Data_pairs, Data_pairs[,i]~group, paired = TRUE)
         result
}     

#        Error: Can't extract columns that don't exist.
#        x Column `group` doesn't exist.



## If I use the following codes for the wilcoxon test, the above loop gives me an error again:

# 2nd test
      result <- wilcox_test(data=Data_pairs, Data_pairs[,i]~Visit, paired = TRUE)
      result
#       Error: Can't extract columns that don't exist.
#       x Column `Data_pairs[, i]` doesn't exist.
   
     

# 3rd test (using wilcox.test function)
        result <- wilcox.test(data=Data_pairs, Data_pairs[,i]~group, paired = TRUE)
        result
#       Error in wilcox.test.default(x = c(9.602, 9.01, 4.524, 3.75,  : 
#       'x' and 'y' must have the same length

> dput(Data_pairs)

structure(list(Visit = c("BSL", "BSL", "BSL", "BSL", "BSL", "BSL", 
"BSL", "BSL", "BSL", "BSL", "LV", "LV", "LV", "LV", "LV", "LV", 
"LV", "LV", "LV", "LV"), Var1 = c(NA, 9.602, 9.01, 4.524, 3.75, 
NA, 6.596, 7.065, 6.877, 15.651, NA, 2.225, 7.417, 1.42, NA, 
NA, 2.752, 6.504, 7.594, 6.652), Var2 = c(24.378, 10.08, 0, 17.86, 
8.656, NA, 5.34, 17.801, 3.408, NA, 18.226, 6.605, 15.61, NA, 
15.965, NA, 24.364, 7.371, 14.391, NA), Var3 = c(23.045, 21.624, 
10.858, 9, 22.575, 15.83, 16.956, 16.505, NA, 31.983, 21.009, 
14.191, NA, 1.392, 22.149, 6.701, NA, 27.116, 13.875, 21.985)), class = "data.frame", row.names = c(NA, 
-20L))

对于如何纠正这个问题有什么建议/建议吗？

谢谢！

Answer 1

wilcox_test() 函数似乎只接受列名称作为公式的一部分（例如 lm() 函数就不是这种情况，您指定公式的符号本来可以工作）。

由于我没有 rstatix 包——显然你正在使用的 wilcox_test() 函数已定义（https://www.rdocumentation.org/packages/rstatix/versions/0.7.0/topics/wilcox_test）——我只能建议你从列名构造公式为如下：

cols = colnames(Data_pairs)
for (i in (2:ncol(Data_pairs))) {
        formula = as.formula( paste(cols[i], cols[1], sep="~") )
        result <- wilcox_test(data=Data_pairs, formula=formula, paired=TRUE)
        result
}

关于您还尝试使用的wilcox.test() 函数：此函数不接受公式，因为它的签名格式为wilcox.test(x, y, ...)，其中x 和y 是分析变量。此外，x 和 y 两个变量都必须是数字，它们不能像 wilcox_test() 函数中的 group 变量那样是因子。 （参考：https://www.rdocumentation.org/packages/stats/versions/3.6.2/topics/wilcox.test）