[R] subsetting

[David Winsemius]

On May 30, 2010, at 11:14 AM, ANJAN PURKAYASTHA wrote:

> Hi,
> I have a data-frame,  r (column names below), that needs subsetting:
> date, time, strain, gene, deltact
>
> When I try to subset r by applying selection criteria on two columns  
> I get
> an empty data frame. For example I would like to extract all rows  
> that have
> time == 0h and strain == ROC.
> So, t <- subset(r, (r$time == "0h" && r$strain == "ROC"),

At least one error is the use of && instead of &. "&&" will only  
return a single value whereas "&" is the correct operator to use when  
working with vectors.

> select= c(time,
> strain, gene, deltact)) returns an empty data-frame.
> Is it not possible to subset based on two criteria?
> TIA
> Anjan
>
> -- 
> ===================================
> anjan purkayastha, phd.
> research associate
> fas center for systems biology,
> harvard university
> 52 oxford street
> cambridge ma
> phone-703.740.6939
> ===================================
>
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>
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David Winsemius, MD
West Hartford, CT