R help - Aug 2010 - loop for inserting rows in a matrix

Dear R friends,
 
I have a matrix with 2060 rows and 41 columns. One column is Date, another is
Transect, and another is Segment. I want to ensure that there are 9 Transects (1
to 9) for each Date, and 8 Segments (1 to 8) for each Transect in the matrix, by
inserting rows where these are missing.
 
I am new to coding, but am trying to write a loop which checks if each of the
transects already exists, and then adds a row in the appropriate place if it
doesn't (I have not tackled the segment part, since I am having problems
with the Transect part). I have simplified the matrix to show the code I so far
have. The code seems to do the right thing for the first date, but not on
subsequent dates. The code is:
 
AerialSurveysm<-matrix(c("13/06/2006","19/06/2006","19/06/2006","19/06/2006","19/06/2006","19/06/2006","26/06/2006",4,7,7,7,8,8,3,
2,5,5,4,4,5,2), nrow = 7, ncol = 3)
colnames(AerialSurveysm) <-
c("Date","Transect","Segment")
 
i=1   #start iteration for all dates
k=2   #start iteration for all transects
m<-unique(AerialSurveysm[,1])

for (i in 1:length(m)) {      #for each date
    for (k in 1:9) {         #do the following for the total number of transects
that there are (1 to 9)
     NewDat <-subset(AerialSurveysm, AerialSurveysm[,1]== m[i])    #select
date to work on beginning with 1st
     indx<-which(AerialSurveysm[,1]==m[i])
     indx<-indx[[1]]        
     Check<-which(NewDat[,2]==k)
     NewRow<-c(c(m[i]),k,0)
      if(is.empty(Check)==TRUE)#if the selected date does not have a transect
equal to transect k
        AerialSurveysm<-insertRow(AerialSurveysm,indx,NewRow) #add a row to
AerialSurveys.m in the location of the correct date
     }
  i=i+1
}
 
Thanks for any hints or thoughts on this (maybe I'm tackling it completely
the wrong way!)!
 
Chandra
 
 
 

	[[alternative HTML version deleted]]

Hi

First of all, use data frame instead of matrix. Matrix is vector with 
dimensions and hence it can not have mixed values  (numeric, character, 
date..).

So let's ASDF is your whole data frame

ASDF<-data.frame(Date=c("13/06/2006","19/06/2006","19/06/2006","19/06/2006","19/06/2006","19/06/2006","26/06/2006"),Trans=c(4,7,7,7,8,8,3),
Segm=c(2,5,5,4,4,5,2), some.data=rnorm(7))

Make whole desired output structure

whole<-expand.grid(Trans=1:9, Segm=1:8, Date=levels(DF$Date))

merged<-merge(whole, ASDF, all.x=TRUE)

Merge your data frame to required structure. Feel free to order it 
according to your desire.

Regards
Petr



r-help-bounces at r-project.org napsal dne 13.08.2010 08:37:38:
> Dear R friends,
> 
> I have a matrix with 2060 rows and 41 columns. One column is Date, 
another is 
> Transect, and another is Segment. I want to ensure that there are 9 
Transects 
> (1 to 9) for each Date, and 8 Segments (1 to 8) for each Transect in the 
> matrix, by inserting rows where these are missing. 
> 
> I am new to coding, but am trying to write a loop which checks if each 
of the 
> transects already exists, and then adds a row in the appropriate place 
if it 
> doesn't (I have not tackled the segment part, since I am having
problems
with 
> the Transect part). I have simplified the matrix to show the code I so 
far 
> have. The code seems to do the right thing for the first date, but not 
on 
> subsequent dates. The code is:
> 
>
AerialSurveysm<-matrix(c("13/06/2006","19/06/2006","19/06/2006","19/06/
>
2006","19/06/2006","19/06/2006","26/06/2006",4,7,7,7,8,8,3,
2,5,5,4,4,5,2), 
> nrow = 7, ncol = 3)
> colnames(AerialSurveysm) <-
c("Date","Transect","Segment")
> 
> i=1   #start iteration for all dates
> k=2   #start iteration for all transects
> m<-unique(AerialSurveysm[,1])
> 
> for (i in 1:length(m)) {      #for each date
>     for (k in 1:9) {         #do the following for the total number of 
> transects that there are (1 to 9)
>      NewDat <-subset(AerialSurveysm, AerialSurveysm[,1]== m[i]) #select 
> date to work on beginning with 1st
>      indx<-which(AerialSurveysm[,1]==m[i])
>      indx<-indx[[1]] 
>      Check<-which(NewDat[,2]==k)
>      NewRow<-c(c(m[i]),k,0)
>       if(is.empty(Check)==TRUE)#if the selected date does not have a 
transect 
> equal to transect k
>         AerialSurveysm<-insertRow(AerialSurveysm,indx,NewRow) #add a row
to 
> AerialSurveys.m in the location of the correct date
>      }
>   i=i+1
> }
> 
> Thanks for any hints or thoughts on this (maybe I'm tackling it 
completely the
> wrong way!)! 
> 
> Chandra
> 
> 
> 
> 
>    [[alternative HTML version deleted]]
> 
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