Select rows of a matrix that meet a condition

Question

In R with a matrix:

     one two three four
 [1,]   1   6    11   16
 [2,]   2   7    12   17
 [3,]   3   8    11   18
 [4,]   4   9    11   19
 [5,]   5  10         


        

Answer 1

If the dataset is called data, then all the rows meeting a condition where value of column 'pm2.5' > 300 can be received by -

data[data['pm2.5'] >300,]