[R] Survey Design / Rake questions

Thomas Lumley tlumley at u.washington.edu
Sat Aug 23 18:38:06 CEST 2008


On Fri, 22 Aug 2008, Farley, Robert wrote:

> I *think* I'm making progress, but I'm still failing at the same step.  My rake call fails with:
> Error in postStratify.survey.design(design, strata[[i]], population.margins[[i]],  :
>  Stratifying variables don't match
>
> To my naïve eyes, it seems that my factors are "in the wrong order".  If so, 
>how do I "assert" an ordering in my survey dataframe, or copy an "image" from 
>the survey dataframe to my marginals dataframes?  I'd prefer to "pull" the 
>original marginals dataframe(s) from the survey dataframe so that I can 
>automate that in production.

It looks like a problem with the NumStn factor. One copy has been converted to character and then factor, giving levels in alphabetical order; the other copy has been converted directly to factor, giving levels in numerical order.

If you use as.factor(1:12) rather than as.character(1:12) it should work.

      -thomas



> If that's not my problem, where might I look for enlightenment?  Neither "?why" nor ?whatamimissing return citations.  :-)
>
>
> **************************************************************************
> **** How I fail Now ******************************************************
> SurveyData <- read.spss("C:/Data/R/orange_delivery.sav", use.value.labels=TRUE, max.value.labels=Inf, to.data.frame=TRUE)
>> #===============================================================================
>> temp <- sub(' +$', '', SurveyData$direction_)
>> SurveyData$direction_ <- temp
>> #===============================================================================
>> SurveyData$NumStn=abs(as.numeric(SurveyData$lineon)-as.numeric(SurveyData$lineoff))
>> mean(SurveyData$NumStn)
> [1] 6.785276
>> ### Kludge
>> SurveyData$NumStn <- pmax(1,SurveyData$NumStn)
>> mean(SurveyData$NumStn)
> [1] 6.789877
>> SurveyData$NumStn <- as.factor(SurveyData$NumStn)
>> ###
>> EBSurvey <- subset(SurveyData, direction_ == "EASTBOUND" )
>> XTTable <- xtabs(~direction_ , EBSurvey)
>> XTTable
> direction_
> EASTBOUND
>      345
>> WBSurvey <- subset(SurveyData, direction_ == "WESTBOUND" )
>> XTTable <- xtabs(~direction_ , WBSurvey)
>> XTTable
> direction_
> WESTBOUND
>      307
>> #
>> EBDesign <- svydesign(id=~sampn, weights=~expwgt, data=EBSurvey)
>> #   svytable(~lineon+lineoff, EBDesign)
>> StnName     <- c( "Warner Center", "De Soto", "Pierce College", "Tampa", "Reseda", "Balboa", "Woodley", "Sepulveda", "Van Nuys", "Woodman", "Valley College", "Laurel Canyon", "North Hollywood")
>> EBOnNewTots <- c(            1000,       600,             1200,     500,     1000,      500,       200,         250,       1000,       300,              100,          123.65,                0 )
>> StnTraveld  <- c(as.character(1:12))
>> EBNumStn    <- c(673.65,     800, 1000, 1000,  800,  700,  600, 500, 400, 200,  50, 50 )
>> ByEBOn  <- data.frame(StnName,   Freq=EBOnNewTots)
>> ByEBNum <- data.frame(StnTraveld, Freq=EBNumStn)
>> RakedEBSurvey <- rake(EBDesign, list(~lineon, ~NumStn), list(ByEBOn, ByEBNum) )
> Error in postStratify.survey.design(design, strata[[i]], population.margins[[i]],  :
>  Stratifying variables don't match
>>
>> str(EBSurvey$lineon)
> Factor w/ 13 levels "Warner Center",..: 3 1 1 1 2 13 1 5 1 5 ...
>> EBSurvey$lineon[1:5]
> [1] Pierce College Warner Center  Warner Center  Warner Center  De Soto
> Levels: Warner Center De Soto Pierce College Tampa Reseda Balboa Woodley Sepulveda Van Nuys Woodman Valley College Laurel Canyon North Hollywood
>> str(ByEBOn$StnName)
> Factor w/ 13 levels "Balboa","De Soto",..: 11 2 5 8 6 1 12 7 10 13 ...
>> ByEBOn$StnName[1:5]
> [1] Warner Center  De Soto        Pierce College Tampa          Reseda
> Levels: Balboa De Soto Laurel Canyon North Hollywood Pierce College Reseda Sepulveda Tampa Valley College Van Nuys Warner Center Woodley Woodman
>>
>> str(EBSurvey$NumStn)
> Factor w/ 12 levels "1","2","3","4",..: 10 12 4 12 8 1 8 8 12 4 ...
>> EBSurvey$NumStn[1:5]
> [1] 10 12 4  12 8
> Levels: 1 2 3 4 5 6 7 8 9 10 11 12
>> str(ByEBNum$StnTraveld)
> Factor w/ 12 levels "1","10","11",..: 1 5 6 7 8 9 10 11 12 2 ...
>> ByEBNum$StnTraveld[1:5]
> [1] 1 2 3 4 5
> Levels: 1 10 11 12 2 3 4 5 6 7 8 9
>>
>
> **************************************************************************
> **************************************************************************
>
>
> Robert Farley
> Metro
> www.Metro.net
>
>
> -----Original Message-----
> From: Thomas Lumley [mailto:tlumley at u.washington.edu]
> Sent: Thursday, August 21, 2008 13:55
> To: Farley, Robert
> Cc: r-help at r-project.org
> Subject: Re: [R] Survey Design / Rake questions
>
> On Tue, 19 Aug 2008, Farley, Robert wrote:
>
>> While I'm trying to catch up on the statistical basis of my task, could
>> someone point me to how I should fix my R error?
>
> The variables in the formula in rake() need to be the raw variables in the
> design object, not summary tables.
>
>       -thomas
>
>>
>> Thanks
>>
>>
>> ########################################################################
>> ####
>>> library(survey)
>>> SurveyData <- read.spss("C:/Data/R/orange_delivery.sav",
>> use.value.labels=TRUE, max.value.labels=Inf, to.data.frame=TRUE)
>>>
>> #=======================================================================
>> ========
>>> temp <- sub(' +$', '', SurveyData$direction_)
>>> SurveyData$direction_ <- temp
>>>
>> #=======================================================================
>> ========
>>>
>> SurveyData$NumStn=abs(as.numeric(SurveyData$lineon)-as.numeric(SurveyDat
>> a$lineoff))
>>> EBSurvey <- subset(SurveyData, direction_ == "EASTBOUND" )
>>> XTTable <- xtabs(~direction_ , EBSurvey)
>>> XTTable
>> direction_
>> EASTBOUND
>>      345
>>> WBSurvey <- subset(SurveyData, direction_ == "WESTBOUND" )
>>> XTTable <- xtabs(~direction_ , WBSurvey)
>>> XTTable
>> direction_
>> WESTBOUND
>>      307
>>> #
>>> EBDesign <- svydesign(id=~sampn, weights=~expwgt, data=EBSurvey)
>>> #   svytable(~lineon+lineoff, EBDesign)
>>> OnLabels    <- c( "Warner Center", "De Soto", "Pierce College",
>> "Tampa", "Reseda", "Balboa", "Woodley", "Sepulveda", "Van Nuys",
>> "Woodman", "Valley College", "Laurel Canyon", "North Hollywood")
>>> EBOnNewTots <- c(            1000,       600,             1200,
>> 500,     1000,      500,       200,         250,       1000,       300,
>> 100,              50,            73.65 )
>>> EBNumStn <- c(673.65,     800, 1000, 1000,  800,  700,  600, 500, 400,
>> 200,  50, 50 )
>>> ByEBOn <- data.frame(OnLabels,EBOnNewTots)
>>> ByEBNum <- data.frame(c(1:12),EBNumStn)
>>> RakedEBSurvey <- rake(EBDesign, list(~ByEBOn, ~ByEBNum),
>> list(EBOnNewTots, EBNumStn ) )
>> Error in model.frame.default(margin, data = design$variables) :
>>  invalid type (list) for variable 'ByEBOn'
>>>
>>
>> ###################################################################
>> sessionInfo()
>> R version 2.7.1 (2008-06-23)
>> i386-pc-mingw32
>>
>> locale:
>> LC_COLLATE=English_United States.1252;LC_CTYPE=English_United
>> States.1252;LC_MONETARY=English_United
>> States.1252;LC_NUMERIC=C;LC_TIME=English_United States.1252
>>
>> attached base packages:
>> [1] graphics  grDevices utils     datasets  stats     methods   base
>>
>>
>> other attached packages:
>> [1] survey_3.8     fortunes_1.3-5 moonsun_0.1    prettyR_1.3-2
>> foreign_0.8-28
>>>
>> ####################################################################
>>
>> Robert Farley
>> Metro
>> www.Metro.net
>>
>> -----Original Message-----
>> From: Farley, Robert
>> Sent: Monday, August 18, 2008 16:18
>> To: 'r-help at r-project.org'
>> Subject: RE: [R] Survey Design / Rake questions
>>
>> Thank you for the list of references.  Do you know of any "free"
>> references available online?  I'll have to find my library card :-)
>>
>>
>> My motivation is to try to correct for a "time on board" bias we see in
>> our surveys.  Not surprisingly, riders who are only on board a short
>> time don't attempt/finish our survey forms.  We're able to weight our
>> survey to the "bus stop-on by bus run" level.  I want to keep that, and
>> rake on new (imposed?) marginals, like an estimate of how many minutes
>> they were on-board derived from their origin-destination.  In practice,
>> we'll have thousands of observations on hundreds of runs.  As I see it,
>> my work-plan involves:
>>
>> 	Running rake successfully on test data
>> 	Preparing "bus stop-on by run" marginals automatically
>> 		Plus any other "pre-existing" marginals to be kept.
>> 	Appending "time on bus" estimates
>> 	Determining the "time on bus" distribution (second survey?)
>> 	Implementing the raking adjustment for a production (large)
>> dataset
>>
>>
>> As of yet, I cannot get the first step to work  :-(
>>
>>
>>
>> I hope there are no "fatal flaws" in this concept....
>>
>>
>>
>>
>>
>> Robert Farley
>> Metro
>> www.Metro.net
>>
>> -----Original Message-----
>> From: Stas Kolenikov [mailto:skolenik at gmail.com]
>> Sent: Monday, August 18, 2008 10:32
>> To: Farley, Robert
>> Cc: r-help at r-project.org
>> Subject: Re: [R] Survey Design / Rake questions
>>
>> Your reading, in increasing order of difficulty/mathematical details,
>> might be Lohr's "Sampling"
>> (http://www.citeulike.org/user/ctacmo/article/1068825), Korn &
>> Graubard's "Health Surveys"
>> (http://www.citeulike.org/user/ctacmo/article/553280), and Sarndal et.
>> al. Survey Math Bible
>> (http://www.citeulike.org/user/ctacmo/article/716032). You certainly
>> should try to get a hold of the primary concepts before collecting
>> your data (or rather before designing your survey... so it might
>> already be too late!). Post-stratification is not that huge topic, for
>> some reason; a review of mathematical details is given by Valliant
>> (1993) (http://www.citeulike.org/user/ctacmo/article/1036976). On
>> raking, the paper on top of Google Scholar search by Deville, Sarndal
>> and Sautory (1993)
>> (http://www.citeulike.org/user/ctacmo/article/3134001) is certainly
>> coming from the best people in the field.
>>
>> I am not aware of general treatment of transportation survey sampling,
>> although I suspect such references do exist in transportation
>> research. There might be particular twists as the same subject/bus
>> usage episode might be sampled at different locations.
>>
>> As far as rake() procedure is concerned, you need to have your data
>> set up as sampled observations with two classifications across which
>> you will be raking, probably the directions "E"/"W" and the stations.
>> Those are not different data.frames, as you are trying to set them up,
>> but a single data.frame with several columns. In other words, your
>> sampled data will have labels "E"/"W" in one of the columns, and
>> station names in another column, and (the names of) those columns will
>> be the imputs of rake().
>>
>> On 8/18/08, Farley, Robert <FarleyR at metro.net> wrote:
>>> I'm trying to learn how to calibrate/postStratify/rake survey data in
>>>  preparation for a large survey effort we're about to embark upon.  As
>> a
>>>  working example, I have results from a small survey of ~650
>> respondents,
>>>  ~90 response fields each.  I'm trying to learn how to (properly?)
>> apply
>>>  the aforementioned functions.
>>>
>>>  My data are from a bus on board survey.  The expansion in the dataset
>> is
>>>  derived from three elements:
>>>
>>>   Response rates by bus stop for a sampled run
>>>
>>>   Total runs/samples runs
>>>
>>>   Normalized to (separately derived) daily line boarding
>>>
>>>  In order to get to the point of raking the data, I need to learn more
>>>  about the survey package and nomenclature.  For instance, given how
>> I've
>>>  described the survey/weighting, is my call to svydesign correct?  I'm
>>>  not sure I understand just what a "survey design" is.  Where can I
>> read
>>>  up on this?  What's a good reference for such things as "PSUs",
>> "cluster
>>>  sampling", and so on.
>>
>> --
>> Stas Kolenikov, also found at http://stas.kolenikov.name
>> Small print: I use this email account for mailing lists only.
>>
>> ______________________________________________
>> 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.
>>
>
> Thomas Lumley			Assoc. Professor, Biostatistics
> tlumley at u.washington.edu	University of Washington, Seattle
>
> ______________________________________________
> 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.
>

Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle



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