[R] Trouble retrieving the second largest value from each row of a data.frame
David Winsemius
dwinsemius at comcast.net
Sun Jul 25 03:27:17 CEST 2010
On Jul 24, 2010, at 8:09 PM, David Winsemius wrote:
>
> On Jul 24, 2010, at 4:54 PM, <mpward at illinois.edu> wrote:
>
>> THANKS, but I have one issue and one question.
>>
>> For some reason the "secondstrongest" value for row 3 and 6 are
>> incorrect (they are the strongest) the remaining 10 are correct??
>
> In my run of Wiley's code I instead get identical values for rows
> 2,5,6. Holtman's and my solutions did not suffer from that defect,
> although mine suffered from my misreading of your request, thinking
> that you wanted the top 3. The fix is trivial
>>
>> These data are being used to track radio-tagged birds, they are
>> from automated radio telemetry receivers. I will applying the
>> following formula
>>
>> diff <- ((strongest- secondstrongest)/100)
>> bearingdiff <-30-(-0.0624*(diff**2))-(2.8346*diff)
>
> vals <- c("value0", "value60", "value120", "value180", "value240",
> "value300")
> value.str2 <- (match(yourdata$secondstrongestantenna, vals)-1)*60
> value.str1 <- (match(yourdata$strongestantenna, vals)-1)*60
> change.ind <- abs(match(yourdata, vals) - which(match(yourdata,
> vals) )
OOOPs should have been
change.ind <- abs(match(yourdata, vals) - match(yourdata, vals) )
>
>>
>> A) Then the bearing diff is added to strongestantenna (value0 =
>> 0degrees) if the secondstrongestatenna is greater (eg value0 and
>> value60),
>
>> B) or if the secondstrongestantenna is smaller than the
>> strongestantenna,
>> then the bearingdiff is substracted from the strongestantenna.
yourdata$finalbearing <- with(yourdata, ifelse (value.str2>value.str1,
bearingdiff+value.str1, value.str1-bearingdiff) )
>
>>
>> C) The only exception is that if value0 (0degrees) is strongest and
>> value300(360degrees) is the secondstrongestantenna then the bearing
>> is 360-bearingdiff.
>
yourdata$finalbearing <- with(yourdata, ifelse (strongestantenna ==
"value0" & secondstrongantenna == "value300", 360- bearingdiff,
finalbearing) );
>> D) Also the strongestantenna and secondstrongestantenna have to be
>> next to each other (e.g. value0 with value60, value240 with
>> value300, value0 with value300) or the results should be NA.
>
> After setting finalbearing with A, B, and C then:
> yourdata$finalbearing <- with(yourdata, ifelse (
> change.ind <5 & change.ind > 1 ,
> NA, finalbearing) )
> yourdata
strongest secondstrongest strongestantenna secondstrongantenna
finalbearing
1 -11072 -11707 value120 value60
-11086.52
2 -11176 -11799 value120 value180
-11190.76
3 -11113 -11778 value120 value60
-11126.91
4 -11071 -11561 value120
value240 NA
5 -11067 -11638 value120 value180
-11082.85
6 -11068 -11698 value0 value60
-11082.62
7 -11092 -11607 value120
value240 NA
8 -11061 -11426 value120
value240 NA
9 -11137 -11736 value120 value60
-11152.26
10 -11146 -11779 value300 value0
-11160.56
>
>> I have been trying to use a series of if,else statements to produce
>> these bearing,
ifelse is the correct construct for processing vectors
--
David.
>> but all I am producing is errors. Any suggestion would be
>> appreciated.
>
>
>>
>> Again THANKS for you efforts.
>>
>> Mike
>>
>> ---- Original message ----
>>> Date: Fri, 23 Jul 2010 23:01:56 -0700
>>> From: Joshua Wiley <jwiley.psych at gmail.com>
>>> Subject: Re: [R] Trouble retrieving the second largest value from
>>> each row of a data.frame
>>> To: mpward at illinois.edu
>>> Cc: r-help at r-project.org
>>>
>>> Hi,
>>>
>>> Here is a little function that will do what you want and return a
>>> nice output:
>>>
>>> #Function To calculate top two values and return
>>> my.finder <- function(mydata) {
>>> my.fun <- function(data) {
>>> strongest <- which.max(data)
>>> secondstrongest <- which.max(data[-strongest])
>>> strongestantenna <- names(data)[strongest]
>>> secondstrongantenna <- names(data[-strongest])[secondstrongest]
>>> value <- matrix(c(data[strongest], data[secondstrongest],
>>> strongestantenna, secondstrongantenna), ncol =4)
>>> return(value)
>>> }
>>> dat <- apply(mydata, 1, my.fun)
>>> dat <- t(dat)
>>> dat <- as.data.frame(dat, stringsAsFactors = FALSE)
>>> colnames(dat) <- c("strongest", "secondstrongest",
>>> "strongestantenna", "secondstrongantenna")
>>> dat[ , "strongest"] <- as.numeric(dat[ , "strongest"])
>>> dat[ , "secondstrongest"] <- as.numeric(dat[ , "secondstrongest"])
>>> return(dat)
>>> }
>>>
>>>
>>> #Using your example data:
>>>
>>> yourdata <- structure(list(value0 = c(-13007L, -12838L, -12880L,
>>> -12805L,
>>> -12834L, -11068L, -12807L, -12770L, -12988L, -11779L), value60 =
>>> c(-11707L,
>>> -13210L, -11778L, -11653L, -13527L, -11698L, -14068L, -11665L,
>>> -11736L, -12873L), value120 = c(-11072L, -11176L, -11113L, -11071L,
>>> -11067L, -12430L, -11092L, -11061L, -11137L, -12973L), value180 =
>>> c(-12471L,
>>> -11799L, -12439L, -12385L, -11638L, -12430L, -11709L, -12373L,
>>> -12570L, -12537L), value240 = c(-12838L, -13210L, -13089L, -11561L,
>>> -13527L, -12430L, -11607L, -11426L, -13467L, -12973L), value300 =
>>> c(-13357L,
>>> -13845L, -13880L, -13317L, -13873L, -12814L, -13025L, -12805L,
>>> -13739L, -11146L)), .Names = c("value0", "value60", "value120",
>>> "value180", "value240", "value300"), class = "data.frame",
>>> row.names = c("1",
>>> "2", "3", "4", "5", "6", "7", "8", "9", "10"))
>>>
>>> my.finder(yourdata) #and what you want is in a nicely labeled data
>>> frame
>>>
>>> #A potential problem is that it is not very efficient
>>>
>>> #Here is a test using a matrix of 100,000 rows
>>> #sampled from the same range as your data
>>> #with the same number of columns
>>>
>>> data.test <- matrix(
>>> sample(seq(min(yourdata),max(yourdata)), size = 500000, replace =
>>> TRUE),
>>> ncol = 5)
>>>
>>> system.time(my.finder(data.test))
>>>
>>> #On my system I get
>>>
>>>> system.time(my.finder(data.test))
>>> user system elapsed
>>> 2.89 0.00 2.89
>>>
>>> Hope that helps,
>>>
>>> Josh
>>>
>>>
>>>
>>> On Fri, Jul 23, 2010 at 6:20 PM, <mpward at illinois.edu> wrote:
>>>> I have a data frame with a couple million lines and want to
>>>> retrieve the largest and second largest values in each row, along
>>>> with the label of the column these values are in. For example
>>>>
>>>> row 1
>>>> strongest=-11072
>>>> secondstrongest=-11707
>>>> strongestantenna=value120
>>>> secondstrongantenna=value60
>>>>
>>>> Below is the code I am using and a truncated data.frame.
>>>> Retrieving the largest value was easy, but I have been getting
>>>> errors every way I have tried to retrieve the second largest
>>>> value. I have not even tried to retrieve the labels for the
>>>> value yet.
>>>>
>>>> Any help would be appreciated
>>>> Mike
>>>>
>>>>
>>>>> data<-
>>>>> data.frame(value0,value60,value120,value180,value240,value300)
>>>>> data
>>>> value0 value60 value120 value180 value240 value300
>>>> 1 -13007 -11707 -11072 -12471 -12838 -13357
>>>> 2 -12838 -13210 -11176 -11799 -13210 -13845
>>>> 3 -12880 -11778 -11113 -12439 -13089 -13880
>>>> 4 -12805 -11653 -11071 -12385 -11561 -13317
>>>> 5 -12834 -13527 -11067 -11638 -13527 -13873
>>>> 6 -11068 -11698 -12430 -12430 -12430 -12814
>>>> 7 -12807 -14068 -11092 -11709 -11607 -13025
>>>> 8 -12770 -11665 -11061 -12373 -11426 -12805
>>>> 9 -12988 -11736 -11137 -12570 -13467 -13739
>>>> 10 -11779 -12873 -12973 -12537 -12973 -11146
>>>>> #largest value in the row
>>>>> strongest<-apply(data,1,max)
>>>>>
>>>>>
>>>>> #second largest value in the row
>>>>> n<-function(data)(1/(min(1/(data[1,]-max(data[1,]))))+
>>>>> (max(data[1,])))
>>>>> secondstrongest<-apply(data,1,n)
>>>> Error in data[1, ] : incorrect number of dimensions
>>>>>
>>>>
>>>> ______________________________________________
>>>> 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.
>>>>
>>>
>>>
>>>
>>> --
>>> Joshua Wiley
>>> Ph.D. Student, Health Psychology
>>> University of California, Los Angeles
>>> http://www.joshuawiley.com/
>>
>> ______________________________________________
>> 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.
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