[R] select if + other questions

[John Kane]

--- Natalie O'Toole <notoole at mtroyal.ca> wrote:

> Hi,
> 
> i am trying to read a .txt file, do a couple of
> select if statements on my 
> data, and then finally use the ?table function to
> get frequency counts on 
> the data. Specifically, i am looking at answering
> the following question:
> 
> What is the frequency of Grade 7 students in the
> province of Alberta who 
> are smokers?
> 
> I am having some problems:
> 
> 1)i cannot get the column names to show up when
> print to screen

Are you sure they are there?  Try mydata[1,] and see
if you get the names.  

If not just assign the names by using 
names (mydata) <- myVariableNames
> 
> 2)I cannot seem to skip variables properly when i
> choose certain other variables

I don't quite understand what you mean here. 
> 
> 3)i cannot get the combination of Select If
> statements to work to produce 
> a different table with my new criteria

Try subset rather than which. 
subset(mydata, PROV=="AB" & GRADE == 7  & Y_Q10A != 9)

which() is a logical operator and as far as I am aware
only will take a TRUE FALSE reponse

which(mydata$PROV=="AB")  # should work



> Here are the variables
> 
> PUMFID position1 length 5
> PROV position 6 length 2
> GRADE position 9 length 2
> Y_Q10A position 33 length 1
> 
> 
> Y_Q10A has the following 1=yes
>                            2=no
>                           9=skip
> 
> all the others have no skipped or missing values
> 
> Here is my code:
> 
> myfile<-("c:/test2.txt")
> myVariableNames<-c("PUMFID","PROV","GRADE","Y_Q10A")
> myVariableWidths<-c(5,2,2,1)
> 
> 
>  mydata<-read.fwf(
> file=myfile,
> width=myVariableWidths,
> col.names=myVariableNames,
> row.names="PUMFID",
> fill=TRUE,
> strip.white=TRUE)
> 
> 
> print(mydata)
> 
> print( mydata [which(PROV=="AB" & GRADE==7 &
> Y_Q10A<9), ] )
> 
> 
> 
> Any help would be greatly appreciated!!
> 
> Thank-you,
> 
> Nat
> 
>