Thanks a lot!!!


On Mon, Mar 4, 2013 at 12:46 PM, MacQueen, Don <macqueen1@llnl.gov> wrote:

> What Jim said separately is correct, and I would suggest following his
> advice.
> But there are some points worth looking at in your method.
>
> See this example:
>
> > item1 <- item2 <- item3 <- item4 <- 1:4
> >
> > matrix1<-cbind(item1, item2, item3, item4)
> >
> > z <- c(TRUE,TRUE,FALSE,TRUE)
> >
> > matrix2 <- cbind(item1[z], item2[z], item3[z], item4[z])
> >
> > matrix3 <- cbind(item1=item1[z], item2=item2[z],
> +                  item3=item3[z], item4=item4[z])
> >
> > print(matrix1)
>      item1 item2 item3 item4
> [1,]     1     1     1     1
> [2,]     2     2     2     2
> [3,]     3     3     3     3
> [4,]     4     4     4     4
> >
> > print(matrix2)
>      [,1] [,2] [,3] [,4]
> [1,]    1    1    1    1
> [2,]    2    2    2    2
> [3,]    4    4    4    4
> >
> > print(matrix3)
>      item1 item2 item3 item4
> [1,]     1     1     1     1
> [2,]     2     2     2     2
> [3,]     4     4     4     4
>
> Points to consider:
>
> Since your "z" is a vector of logical values, you don't need
>    item1[z==T]
> instead, use
>    item1[z]
>
> Your column names on matrix2 do not look correct, given how you created
> matrix2.
>
> Not that you can specify column names when you create the matrix using
> cbind, as in my matrix3 example.
>
> -Don
>
>
> --
> Don MacQueen
>
> Lawrence Livermore National Laboratory
> 7000 East Ave., L-627
> Livermore, CA 94550
> 925-423-1062
>
>
>
>
>
> On 2/28/13 5:53 PM, "Pablo Menese" <pmenese@gmail.com> wrote:
>
> I'm performing item response theory with eRm packages
> I am excluding the persons that doesn't fit in the infit/outfit persons.
> for that I created a condition. then I have to create a new subset or
> matrix but with the condition.
>
> So:
>
> ORIGINAL
>
> matrix<-cbind(item1, item2, item3, item4)
>
> IF I PERFORM A head(matrix)
>
> item1 item2 item3 item4
>   3         2       3       1
>   3         1       2       4
>
> THEN I CREATE THE LOGIC CONDITION
>
> z<-thing==T
>
> THEN I TRY TO CREATE THE NEW MATRIX BUT WITH THE CONDITION
>
> matrix2<-cbind(item1[z==T], item2[z==T], item3[z==T], item4[z==T])
>
> THE ISSUE IS THAT IF I PERFORM A head(matrix2)
>
>  I1        I2       I3      I4
>   3         2       3       1
>   3         1       2       4
>
> The names of the columns change at all.
>
> CAN ANYONE HELP ME TO KEEP THE SAME NAMES?
>
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>
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