如果行(特定字段)匹配，则awk列的平均部分 [英] awk average part of column if lines (specific field) match

问题描述

这是我的输入文件的示例:

Here is a sample of my input file :

$cat NDVI-bm  
P01 031.RAW 0.516 0 0  
P01 021.RAW 0.449 0 0  
P02 045.RAW 0.418 0 0  
P03 062.RAW 0.570 0 0  
P03 064.RAW 0.469 0 0  
P04 083.RAW 0.636 0 0  
P04 081.RAW 0.592 0 0  
P04 082.RAW 0.605 0 0  
P04 084.RAW 0.648 0 0  
P05 093.RAW 0.748 0 0

如果第一个字段匹配，我需要对第3列取平均值.很简单，但是由于我的awk知识非常基础，所以我很挣扎...这就是我到目前为止所拥有的:

I need to average column 3 if first field match. Simple enough, but I'm struggling as my awk knowledges are quite basics... Here is what I have so far :

awk '{array[$1]+=$3(need to divide here by number of matches...)} END { for (i in array) {print i"," array[i]}}' NDVI-bm

通过搜索网络，我真的不确定自己的前进方向是否正确...除非有一种简便的方法来计算比赛的次数，但我似乎找不到...任何想法?

By searching the web, I'm really not sure I'm heading in the right way... unless there is an easy way to count the number of matches, wich I can't seem to find... Any ideas ?

感谢您的帮助！

推荐答案

例如，计算以"P01"开头的行的平均值:

E.g to calculate the average of lines starting with "P01":

/^P01/{
    num+=1
    cnt+=$3
}
END {print "avg = " cnt/num}

输出:

$ awk -f avg.awk input
avg = 0.4825

...或者，作为一个单行:

...or, as a oneliner:

$ awk '/^P01/{cnt+=$3; num+=1} END{print "avg="cnt/num}' input

或者同时对第一列的所有值进行计算:

Or to do the calculations for all values of the first column simultaneously:

{
    sum[$1]+=$3
    cnt[$1]++
}


END {
    print "Name" "\t" "sum" "\t" "cnt" "\t" "avg"
    for (i in sum)
        print i "\t" sum[i] "\t" cnt[i] "\t" sum[i]/cnt[i]

}

输出:

$ awk -f avg.awk input
Name    sum     cnt     avg
P01     0.965   2       0.4825
P02     0.418   1       0.418
P03     1.039   2       0.5195
P04     2.481   4       0.62025
P05     0.748   1       0.748

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