R help - Apr 2008 - how to read data from table based a condition

Dear All:

    I imported a table into R. But I want to read a variable (y) from this table
conditional on another variable (x=1) in the table.

y<-data[,7]
x<-data[,3]

I want to know the mean of y if corresponding x=1.

I tried 

if (x==1) y3<-y 

It does not work.

Anyone can give a help?

Thanks!


Xin
	[[alternative HTML version deleted]]

Xin <jasonshi510 <at> hotmail.com> writes:

> 
> y<-data[,7]
> x<-data[,3]
> 
> I want to know the mean of y if corresponding x=1.
> 
Try this:

mean(data[data[,3]==1,data[,7])

You can also look at ?subset.

Xin wrote:
> Dear All:
> 
>     I imported a table into R. But I want to read a variable (y) from this
table conditional on another variable (x=1) in the table.
> 
> y<-data[,7]
> x<-data[,3]
> 
> I want to know the mean of y if corresponding x=1.
> 
> I tried 
> 
> if (x==1) y3<-y 
> 
> It does not work.
> 
> Anyone can give a help?
Is this homework?
Please do read the posting guide and An Introduction to R!

Uwe Ligges


 > Thanks!
> 
> 
> Xin
> 	[[alternative HTML version deleted]]
> 
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