R help - Jan 2009 - Relative frequency of cases in data frame matching a specified criteria

I want to get the relative frequency of cases in a data frame that
matches a specified criteria, omiting NA values. This seem so simple,
but I can't come up with an effective way.

nrow(data[data$variable>value & !is.na(data$variable),])/nrow(data)

works but is very ineffective and CPU consuming when the data frame is
large (more than 13000 rows and 400 columns).

/S

in this case you just need:

mean(data$variable > value & !is.na(data$variable))


I hope it helps.

Best,
Dimitris


Stefan Bj?rk wrote:
> I want to get the relative frequency of cases in a data frame that
> matches a specified criteria, omiting NA values. This seem so simple,
> but I can't come up with an effective way.
> 
> nrow(data[data$variable>value & !is.na(data$variable),])/nrow(data)
> 
> works but is very ineffective and CPU consuming when the data frame is
> large (more than 13000 rows and 400 columns).
> 
> /S
> 
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-- 
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus Medical Center

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