R help - Jun 2010 - Subtraction loop

I have a data frame with 2 columns, one for day and one for average.  
The day starts at 97 all the way to 279. I want to subtract day 98  
average- day 97 average, then day99 average -day 98 average and so on  
down my list, creating another column with the subtracted results.
I have:

     Day DailyAverage
1    97    0.6076782
2    98    0.7121478
3    99    0.8059347
4   100    0.9545806
5   101    1.0589791
6   102    1.1335981
7   103    1.2676922
8   104    1.4429847
9   105    1.6477266
10  106    1.7970784
etc. with values to day 279

I'm guessing I need to create some kind of loop for this, but I am  
unsure as to how to do this. Any help is greatly appreciated.

Thanks,
Emilija

Hello,

Check the function diff() it can do it for you, no need for a loop.

Cheers,
Jonas Mandel


ecvetano at uwaterloo.ca a ?crit :
> I have a data frame with 2 columns, one for day and one for average. The
> day starts at 97 all the way to 279. I want to subtract day 98 average-
> day 97 average, then day99 average -day 98 average and so on down my
> list, creating another column with the subtracted results.
> I have:
> 
>     Day DailyAverage
> 1    97    0.6076782
> 2    98    0.7121478
> 3    99    0.8059347
> 4   100    0.9545806
> 5   101    1.0589791
> 6   102    1.1335981
> 7   103    1.2676922
> 8   104    1.4429847
> 9   105    1.6477266
> 10  106    1.7970784
> etc. with values to day 279
> 
> I'm guessing I need to create some kind of loop for this, but I am
> unsure as to how to do this. Any help is greatly appreciated.
> 
> Thanks,
> Emilija
> 
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> and provide commented, minimal, self-contained, reproducible code.
> 
>