R-基于2个变量对数据帧进行子集化（其中一个是随机数，以便对第一个变量进行采样）？

Question

I would like to create a subset of a large data frame. I would like to select one row with each value for column 1 "class", based on having the lowest number for column 2 "random number".

For example, rows 1,2,and 3 all have the value 2 in column 1 and I would like to keep/subset row 3 as it has the lowest random number (3.446456). For this sample I would like to subset rows 3,4,7,8,9,10,11.

My dataset has over 10,000 rows, so is there a way of coding for this? I'm using R studio.

Thanks very much,

Class   Random_number   Score_1      Score_2         Score_3 
2       5.575475        0.78464      0.747847        0.6746464
2       7.738382        0.73273      0.747474        0.6734652
2       3.456456        0.78464      0.747847        0.6746464
3       6.939399        0.23363      0.123555        0.6476384
4       10.99993        0.66654      0.565757        0.6565633
4       6.894898        0.54295      0.825264        0.2357674 
4       5.575475        0.78464      0.747847        0.6746464
5       3.738382        0.73273      0.747474        0.6734652
6       3.456456        0.78464      0.747847        0.6746464
7       6.932119        0.23363      0.123555        0.6476384
7       17.11993        0.66654      0.565757        0.6565633
8       6.895898        0.54295      0.825264        0.2357674

Answer 1

Try ordering the data set by random number :

data<-data[order(data$Random_number),]

Then subset by taking out duplicate values of Class

data<-subset(data, !duplicated(Class))