R help - Nov 2007 - how to find and use specific column after spliting dataframe

Dear all: 


I am a new R-user and I have 2 questions
about it.  


1) I need to find specific sub-dataframe,
and then use specific column to calculate. 
For example, after splitting dataframe, I find specific the
sub-dataframe, such as ?A.split [1]?. 
But, I don?t know how to find ?time? and ?concentration? columns of ?A.split
[1]?.  


2) The equation used to sub-dataframe is
(time[i]-time[i-1])*(concentration[i]- concentration[i-1])*1/2.  I don?t know
how to calculate it.  How can I find the specific column and use it to calculate
?



 


x<-rep(c(1.2,6.8),4)


y<-rep(c(1, 2),4)


z<-rep(c(1,2),4)


t<-rep(c(0,1,2,3),length.out=8)


c<-rep(c(0,0.5,1,2),length.out=8)


df<-data.frame(pH=x, formulation=y,
subject=z, time=t, concentration=c)


A.split<-split(df, list(df$pH
,df$formulation, df$subject) )


A.split [1] 




 


Best regards,


Hsin-Ya Lee






     
______________________________________________________________________________________
??????????????????????????????http://tw.promo.yahoo.com/antispam/index.html

Try this:

A.split[[1]]["time"]
A.split[[1]][["concentration"]]

test <- NULL
for(i in 2:4){
    test[i] <- (A.split[[1]][["time"]][i] -
A.split[[1]][["time"]][i-1]) *
   (A.split[[1]][["concentration"]][i] -
A.split[[1]][["concentration"]][i-1])
* 0.5
}


On 28/11/2007, leeznar <leeznar@yahoo.com.tw>
wrote:
>
>
>
> Dear all:
>
>
> I am a new R-user and I have 2 questions
> about it.
>
>
> 1) I need to find specific sub-dataframe,
> and then use specific column to calculate.
> For example, after splitting dataframe, I find specific the
> sub-dataframe, such as "A.split [1]".
> But, I don't know how to find "time" and
"concentration" columns of
> "A.split
> [1]".
>
>
> 2) The equation used to sub-dataframe is
> (time[i]-time[i-1])*(concentration[i]- concentration[i-1])*1/2.  I
don't
> know how to calculate it.  How can I find the specific column and use it to
> calculate ?
>
>
>
>
>
>
> x<-rep(c(1.2,6.8),4)
>
>
> y<-rep(c(1, 2),4)
>
>
> z<-rep(c(1,2),4)
>
>
> t<-rep(c(0,1,2,3),length.out=8)
>
>
> c<-rep(c(0,0.5,1,2),length.out=8)
>
>
> df<-data.frame(pH=x, formulation=y,
> subject=z, time=t, concentration=c)
>
>
> A.split<-split(df, list(df$pH
> ,df$formulation, df$subject) )
>
>
> A.split [1]
>
>
>
>
>
>
>
> Best regards,
>
>
> Hsin-Ya Lee
>
>
>
>
>
>
>
>
______________________________________________________________________________________
> Ôõ˜ÓœpÉÙÀ¬»øÐÅ£¿Ö»Òª¿´µ½À¬»øÐÅ£¬Á¢¼´°´Ï¡¸ß@ÊÇÀ¬»øÐÅ¡¹°´âo¡£
> http://tw.promo.yahoo.com/antispam/index.html
>
> ______________________________________________
> R-help@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.
>


-- 
Henrique Dallazuanna
Curitiba-Paran¨¢-Brasil
25¡ã 25' 40" S 49¡ã 16' 22" O

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