[R] to append a column to a data frame, has I use loop/if in my case?

[jim holtman]

Here is how you should be creating your dataframe so that each element
has the proper mode:

> days=Sys.Date()-1:70
> price=abs(rnorm(70))
> regular=rep(c(0,0,0,0,1,0,1,0,0,1),c(7,7,7,7,7,7,7,7,7,7))
> y=data.frame(cbind(days,price,regular))
> str(y)
'data.frame':   70 obs. of  3 variables:
 $ days   : num  14991 14990 14989 14988 14987 ... # notice is it numeric
 $ price  : num  0.626 0.184 0.836 1.595 0.33 ...
 $ regular: num  0 0 0 0 0 0 0 0 0 0 ...
> y <- data.frame(days, price, regular)
> str(y)
'data.frame':   70 obs. of  3 variables:
 $ days   :Class 'Date'  num [1:70] 14991 14990 14989 14988 14987 ...#
here it is 'Date'
 $ price  : num  0.626 0.184 0.836 1.595 0.33 ...
 $ regular: num  0 0 0 0 0 0 0 0 0 0 ...
> y
         days      price regular
1  2011-01-17 0.62645381       0
2  2011-01-16 0.18364332       0
3  2011-01-15 0.83562861       0
4  2011-01-14 1.59528080       0
5  2011-01-13 0.32950777       0
6  2011-01-12 0.82046838       0
7  2011-01-11 0.48742905       0
8  2011-01-10 0.73832471       0


On Mon, Jan 17, 2011 at 9:59 AM, Daniel Wu <daniel_wu_r at 163.com> wrote:
> days=Sys.Date()-1:70
> price=abs(rnorm(70))
> regular=rep(c(0,0,0,0,1,0,1,0,0,1),c(7,7,7,7,7,7,7,7,7,7))
> y=data.frame(cbind(days,price,regular))
>
>
> y is like
>    days      price regular
> 1  14990 0.16149463       0
> 2  14989 1.69519358       0
> 3  14988 1.57821998       0
> 4  14987 0.47614311       0
> 5  14986 0.87016180       0
> 6  14985 2.55679229       0
> 7  14984 0.89753533       0
>
>
> the output I want:
> have another column appended to y, whose value is the max price in the recent 2 **regular** weeks.
> So if the current row is today, then get the max price of the past 14 days (including today) if the last 2 week are regular weeks,  if one of the last 2 weeks is not regular week, then I need to go back further to find the max price, as I need the max price for the last 2 **regular** weeks. How can I do that? Or I have to use loop/if to do it?
>
>
>
>
> BTW, why the days is like 14990,14989, after cbind(days,price,regular)? before the cbind, days is like the format "2010-12-23".
>        [[alternative HTML version deleted]]
>
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-- 
Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?