R help - Jun 2008 - splitting data frame based on a criteria

Hi,
I have a data frame that I want to split into two based on the values of a
variable in it.

The variable Y has numeric values ranging between 0 through 70. I want to
plot the frequencies of another variable X in two different cases:
- When Y = 0 and
- When Y > 0

How does one go about doing this?

In general, I want to do several analyses with this data frame that are a
variation of the above situation, i.e. they require splitting the data into
different age, gender etc. and then calculating separate means, correlations
and so on for the different groups into which the data frame would split.

I am struggling with the correct syntax for achieving this.

Reading through the documentation suggests that tapply and split may be the
functions to use for my purposes but the examples in the documentations
didn't help me understand how I could achieve this.

I would appreciate any suggestions and help.

Thanks,
Marvin

	[[alternative HTML version deleted]]

?by may be helpful here
eg if dat is your data.frame and yf is a factor (created using ifelse)
use by(dat,yf,mean) to compute the means for each level of yf
hth, Ingmar

On Jun 3, 2008, at 8:37 PM, Marvin Lists wrote:
> Hi,
> I have a data frame that I want to split into two based on the  
> values of a
> variable in it.
>
> The variable Y has numeric values ranging between 0 through 70. I  
> want to
> plot the frequencies of another variable X in two different cases:
> - When Y = 0 and
> - When Y > 0
>
> How does one go about doing this?
>
> In general, I want to do several analyses with this data frame that  
> are a
> variation of the above situation, i.e. they require splitting the  
> data into
> different age, gender etc. and then calculating separate means,  
> correlations
> and so on for the different groups into which the data frame would  
> split.
>
> I am struggling with the correct syntax for achieving this.
>
> Reading through the documentation suggests that tapply and split  
> may be the
> functions to use for my purposes but the examples in the  
> documentations
> didn't help me understand how I could achieve this.
>
> I would appreciate any suggestions and help.
>
> Thanks,
> Marvin
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting- 
> guide.html
> and provide commented, minimal, self-contained, reproducible code.