[R] Performing operations only on selected data

[Marcel Curlin]

I spent some time on this simple question, also searched the forum,
eventually hacked my way to an ugly solution for my particular problem but I
would like to improve my coding:

I have data of the form:
df <- expand.grid(group=c('copper', 'zinc', 'aluminum', 'nickel'),
condition1=c(1:4))

I would like to add a new data column "condition2", with values equal to the
value of condition1 plus a random number from 0-1 (uniform distribution)  if
the value of condition1 is < 1, or just condition1 if the value of
condition1 is > 1. More generally, my interest is in manipulating the values
of condition1 if they meet one or more criteria, or keeping the values the
same otherwise. Thanks for any thoughts!

 



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