Message-ID: <E66794E69CFDE04D9A70842786030B9331D9F3@PA-MBX04.na.tibco.com>
Date: 2012-09-18T15:12:12Z
From: William Dunlap
Subject: help with calculation from dataframe with multiple entries per sample
In-Reply-To: <1347937901.52268.YahooMailNeo@web142606.mail.bf1.yahoo.com>
The following works even when the input data frame has its rows
scrambled. It does not currently check that there is exactly one entry
in each sample for Time==2 and Time==3.
within(mydata,
`Gain2-3` <- ave(seq_along(Sample),
Sample,
FUN=function(i) {
L2 <- Time[i]==2
L3 <- Time[i]==3
Mass[i][L3] - Mass[i][L2] }))
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
> Of arun
> Sent: Monday, September 17, 2012 8:12 PM
> To: Julie Lee-Yaw
> Cc: R help
> Subject: Re: [R] help with calculation from dataframe with multiple entries per sample
>
> HI,
> Modified version of my earlier solution:
> res1<-tapply(mydata$Mass,mydata$Sample,FUN=function(x) (x[3]-x[2]))
> res2<-data.frame(Sample=names(res1),Gain2_3=res1)
> ?merge(mydata,res2)
>
> #Sample Time Mass Gain2_3
> #1????? 1??? 1? 3.0???? 0.3
> #2????? 1??? 2? 3.1???? 0.3
> #3????? 1??? 3? 3.4???? 0.3
> #4????? 2??? 1? 4.0???? 0.1
> #5????? 2??? 2? 4.3???? 0.1
> #6????? 2??? 3? 4.4???? 0.1
> #7????? 3??? 1? 3.0???? 0.3
> #8????? 3??? 2? 3.2???? 0.3
> #9????? 3??? 3? 3.5???? 0.3
> A.K.
>
>
>
> ----- Original Message -----
> From: Julie Lee-Yaw <julleeyaw at yahoo.ca>
> To: "r-help at r-project.org" <r-help at r-project.org>
> Cc:
> Sent: Monday, September 17, 2012 7:15 PM
> Subject: [R] help with calculation from dataframe with multiple entries per sample
>
> Hi
>
> I have a dataframe similar to:
>
> >Sample<-c(1,1,1,2,2,2,3,3,3)
>
> >Time<-c(1,2,3,1,2,3,1,2,3)
>
> >Mass<-c(3,3.1,3.4,4,4.3,4.4,3,3.2,3.5)
>
> >mydata<-as.data.frame(cbind(Sample,Time,Mass))
>
>
> ? Sample Time Mass
> 1 ? ? ?1 ? ?1 ?3.0
> 2 ? ? ?1 ? ?2 ?3.1
> 3 ? ? ?1 ? ?3 ?3.4
> 4 ? ? ?2 ? ?1 ?4.0
> 5 ? ? ?2 ? ?2 ?4.3
> 6 ? ? ?2 ? ?3 ?4.4
> 7 ? ? ?3 ? ?1 ?3.0
> 8 ? ? ?3 ? ?2 ?3.2
> 9 ? ? ?3 ? ?3 ?3.5
>
> where for each sample, I've measured mass at different points in time.
>
> I now want to calculate the difference between Mass at Time 2 and 3 for each unique
> Sample and store this as a new variable called "Gain2-3". So in my example three values
> of 0.3,0.1,0.3 would be calculated for my three unique samples and these values would
> be repeated in the table according to Sample. I am thus expecting:
>
> >mydata #after adding new variable
>
> ? Sample Time MassGain2-3
> 1 ? ? ?1 ? ?1 ?3.00.3
> 2 ? ? ?1 ? ?2 ?3.1 0.3
> 3 ? ? ?1 ? ?3 ?3.4 0.3
> 4 ? ? ?2 ? ?1 ?4.0 0.1
> 5 ? ? ?2 ? ?2 ?4.3 0.1
> 6 ? ? ?2 ? ?3 ?4.4 0.1
> 7 ? ? ?3 ? ?1 ?3.0 0.3
> 8 ? ? ?3 ? ?2 ?3.2 0.3
> 9 ? ? ?3 ? ?3 ?3.5 0.3
>
> Does anyone have any suggestions as to how to do this? I've looked at the various apply
> functions but I can't seem to make anything work. I'm fairly new to R and would
> appreciate specific suggestions.
>
> Thanks!
> ??? [[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.
>
>
> ______________________________________________
> 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.