Error in apply(df$var1, 2, mean) : dim(X) must have a positive length
目录
Error in apply(df$var1, 2, mean) : dim(X) must have a positive length
问题：
出现错误是因为apply（）函数必须应用于dataframe或matrix，我们尝试将其应用于数据帧中的特定列则发生错误。
#create data frame
df <- data.frame(points="c(99," 97, 104, 79, 84, 88, 91, 99), rebounds="c(34," 40, 41, 38, 29, 30, 22, 25), blocks="c(12," 8, 7, 11, 6, 7)) #view data frame df #attempt to calculate mean of 'points' column apply(df$points, 2, mean)< code></->
解决：
计算所有列的均值
#calculate mean of every column in data frame
apply(df, 2, mean)
points rebounds blocks
92.625 32.375 8.375
计算部分列的均值
#calculate mean of 'points' and 'blocks' column in data frame
apply(df[c('points', 'blocks')], 2, mean)
points blocks
92.625 8.375
计算其中一列的均值
#calculate mean of 'points' column
mean(df$points)
[1] 92.625
完整错误：
create data frame
df
Original: https://blog.csdn.net/zhongkeyuanchongqing/article/details/120626262
Author: Data+Science+Insight
Title: Error in apply(df$var1, 2, mean) : dim(X) must have a positive length
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