如何根据R中的ID对列进行平均? [英] How to average columns based on ID in R?

问题描述

我想按其ID取平均值，但并非所有ID都具有相同数量的值.如何在R中执行此操作?

I want to average the values by their IDs but not all ID's have the same number of values. How do I do this in R?

我有两列ID和值

    ID    Value
    1000    0.51
    1000    0.01
    1001    0.81
    1001    0.41
    1001    0.62
    1002    0.98
    1002    0.12
    1002    0.15
    1003    0.12
    ...     ...

推荐答案

您可以尝试by():

> with(df, by(Value, ID, mean))
# ID: 1000
# [1] 0.26
# ------------------------------------------------------------ 
# ID: 1001
# [1] 0.6133333
# ------------------------------------------------------------ 
# ID: 1002
# [1] 0.4166667
# ------------------------------------------------------------ 
# ID: 1003
# [1] 0.12

或aggregate():

> aggregate( Value ~ ID, df, mean)
#     ID     Value
# 1 1000 0.2600000
# 2 1001 0.6133333
# 3 1002 0.4166667
# 4 1003 0.1200000

或使用data.table(如果您需要对大型数据集进行快速计算):

or using data.table (if you need fast calculation on large data sets):

> library(data.table)
> setDT(df)[, mean(Value), by = ID]
#      ID        V1
# 1: 1000 0.2600000
# 2: 1001 0.6133333
# 3: 1002 0.4166667
# 4: 1003 0.1200000

数据

df <- structure(list(ID = c(1000L, 1000L, 1001L, 1001L, 1001L, 1002L, 
1002L, 1002L, 1003L), Value = c(0.51, 0.01, 0.81, 0.41, 0.62, 
0.98, 0.12, 0.15, 0.12)), .Names = c("ID", "Value"), 
class = "data.frame", row.names = c(NA, -9L))

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