[R] Newbie: Better way to do compound conditionals in subset?

[Jeffrey Robert Spies]

I would personally use the following method (example using the iris  
data included with R):

data(iris)
tSelect <- (iris$Sepal.Length > 6.0 & iris$Sepal.Length < 6.2 & iris 
$Sepal.Width == 3.0)
tSelectedData <- iris[tSelect,]

Then  you can simply work with tSelectedData for whatever equation  
you use, i.e.:

tSelectedData$Sepal.Length - tSelectedData$Sepal.Width

Of course you could write all of this on one line, but that doesn't  
read well.

Hope that helps,

Jeff.

On Oct 26, 2006, at 3:55 PM, Zembower, Kevin wrote:

> There must be a better way to select the rows after 22-Apr-2004 and
> before 01-Sep-2004 with a temperature below 65 than this:
>
>> before2sw1 <- subset(energy.data, as.Date(start, format="%d-%b-%y") <
> as.Date("01-Sep-04", format = "%d-%b-%y"))
>> before2sw2 <- subset(before2sw1, as.Date(start, format="%d-%b-%y") >=
> as.Date("22-Apr-04", format = "%d-%b-%y"), select=c(therms,temp,days))
>> before2sw <- subset(before2sw2, temp < 65)
>
> Is it also possible to combine in this step:
>
> attach(before2sw)
> before2sw.HDD <- therms / (65 - temp) * days
>
> My data looks like this:
>> head(energy.data)
>       start therms   gas KWHs elect temp days
> 1 10-Jun-98      9 16.84  613 63.80   75   40
> 2 20-Jul-98      6 15.29  721 74.21   76   29
> 3 18-Aug-98      7 15.73  597 62.22   76   29
> 4 16-Sep-98     42 35.81  460 43.98   70   33
> 5 19-Oct-98    105 77.28  314 31.45   57   29
> 6 17-Nov-98    106 77.01  342 33.86   48   30
>>
>
> Thanks for your suggestions and advice. I'm continuing to enjoy  
> learning
> R.
>
> -Kevin
>
> Kevin Zembower
> Internet Services Group manager
> Center for Communication Programs
> Bloomberg School of Public Health
> Johns Hopkins University
> 111 Market Place, Suite 310
> Baltimore, Maryland  21202
> 410-659-6139
>
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