[R] problem with function that adds rows to dataframe based on conditional statement

[PIKAL Petr]

Hi

May I ask you why do you need such operation. I cannot imagine a situation where I would need to do this. The only imaginable procedure is to merge NA enhanced object with another object but for that situation usually

?merge

is used

Cheers
Petr

> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Curtis
> Burkhalter
> Sent: Thursday, March 05, 2015 9:42 PM
> To: r-help at r-project.org
> Subject: [R] problem with function that adds rows to dataframe based on
> conditional statement
>
> Hello everyone,
>
> I'm having a problem with a function that I wrote that is supposed to
> add a
> row to dataframe based upon a conditional statement. To explain I've
> used
> an example below:
>
> #create data frame
> animals=c("bird","dog","cat")
> animals=rep(animals,each=4)
> animals=animals[1:11]
> animalYears=c(1,1,2,2,1,1,2,2,1,1,2)
> animalMass=round(runif(11,min=10,max=50),0)
>
> comAn=as.data.frame(cbind(animals,animalYears,animalMass))
> comAn
>
>   * animals* *animalYears* *animalMass*
> 1     bird           1         30
> 2     bird           1         32
> 3     bird           2         27
> 4     bird           2         16
> 5      dog           1         22
> 6      dog           1         25
> 7      dog           2         41
> 8      dog           2         22
> 9      cat           1         30
> 10     cat           1         37
> 11     cat           2         49
>
> We can see here that for every type of animal I have two years of mass
> measurements, except for the cat in year 2. What I want to do is add an
> additional row to the end of the dataframe that consists strictly of
> NAs
> and then I can substitute those out later.
>
> So what I first did was split the 'comAn' dataframe into the different
> Animal by Year combos.
>
> #This line splits 'com_An' into a list ordered by the Animal by Year
> combos
> comAn_split=split(comAn, paste(comAn$animals,comAn$animalYear))
>
> Then I wrote the function that identifies whether a particular Animal
> by
> Year combo is less than two rows in length and if so it should add
> another
> row that consists only of NAs using the vector 'NAs':
>
> #This function identifies the length of each Animal by Year combo and
> then
> #uses the rbind function built in R to add a row
> #to each animal by year combo if they have less than 2 samples
>
> addNA <- function(comAn) {
>   NAs=c(NA,NA,NA)
>         ind <- seq_len(nrow(comAn))
>         comAn[ifelse(length(ind)<2,rbind(NAs),length(ind)),]
> }
>
> #This applies the function addNs to the animals data organized in list
> format
> addedNAcomAn <- do.call(rbind, lapply(comAn_split, addNA))
> addedNAcomAn
>
> When I apply the function to the list of the different Animal by Year
> combos this is what I get:
>        animals animalYears animalMass
> bird 1    bird           1         23
> bird 2    bird           2         50
> cat 1      cat           1         15
> cat 2     <NA>        <NA>       <NA>
> dog 1      dog           1         23
> dog 2      dog           2         38
>
> What I expect is this:
>
>    animals animalYears animalMass
> 1     bird           1         41
> 2     bird           1         23
> 3     bird           2         23
> 4     bird           2         50
> 5      dog           1         49
> 6      dog           1         23
> 7      dog           2         13
> 8      dog           2         38
> 9      cat           1         42
> 10     cat           1         15
> 11     cat           2         33
> 12     NA           NA      NA
>
> Am I conditioning improperly within the function or am I missing
> something
> else. Any help would be greatly appreciated.
>
> Best
>
> --
> Curtis Burkhalter
>
>       [[alternative HTML version deleted]]
>
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