[R] princomp - how to take out part result

[David Winsemius]

On Feb 7, 2009, at 9:07 AM, Nash wrote:

> Dear all, i have two problems
>
> if i have a principal components analysis report as follows:
>
> ?princomp
>
> problem one.
>
>> pc.cr <- princomp(USArrests, cor = TRUE)
>> pc.cr
>
> i want to export a txt file (*.txt) to save "pc.cr" report
> ###########################################
> Call:
> princomp(x = USArrests, cor = TRUE)
>
> Standard deviations:
>   Comp.1    Comp.2    Comp.3    Comp.4
> 1.5748783 0.9948694 0.5971291 0.4164494
>
> 4  variables and  50 observations.
> ###########################################
> what can i do ?

?sink


>
>
> -----------------------------------------------------------
> problem two.
>
>> load  <- loadings(pc.cr)
>> load
>
> Loadings:
>         Comp.1 Comp.2 Comp.3 Comp.4
> Murder   -0.536  0.418 -0.341  0.649
> Assault  -0.583  0.188 -0.268 -0.743
> UrbanPop -0.278 -0.873 -0.378  0.134
> Rape     -0.543 -0.167  0.818
>
>               Comp.1 Comp.2 Comp.3 Comp.4
> SS loadings      1.00   1.00   1.00   1.00
> Proportion Var   0.25   0.25   0.25   0.25
> Cumulative Var   0.25   0.50   0.75   1.00
>
> i want to take out matrix
>
>               Comp.1 Comp.2 Comp.3 Comp.4
> SS loadings      1.00   1.00   1.00   1.00
> Proportion Var   0.25   0.25   0.25   0.25
> Cumulative Var   0.25   0.50   0.75   1.00
>
> what can i do ?

When you look at load with str(), you only see the loadings matrix and  
not the rest of what you thought was a "result", which means to me  
that the print method for that class of object is doing something  
behind the scenes.  See the method thusly:

 > getAnywhere(print.loadings)
A single object matching ‘print.loadings’ was found
It was found in the following places
   registered S3 method for print from namespace stats
   namespace:stats
with value

function (x, digits = 3, cutoff = 0.1, sort = FALSE, ...)
{
     Lambda <- unclass(x)
     p <- nrow(Lambda)
     factors <- ncol(Lambda)
     if (sort) {
         mx <- max.col(abs(Lambda))
         ind <- cbind(1:p, mx)
         mx[abs(Lambda[ind]) < 0.5] <- factors + 1
         Lambda <- Lambda[order(mx, 1:p), ]
     }
     cat("\nLoadings:\n")
     fx <- format(round(Lambda, digits))
     names(fx) <- NULL
     nc <- nchar(fx[1], type = "c")
     fx[abs(Lambda) < cutoff] <- paste(rep(" ", nc), collapse = "")
     print(fx, quote = FALSE, ...)
     vx <- colSums(x^2)
     varex <- rbind(`SS loadings` = vx)
     if (is.null(attr(x, "covariance"))) {
         varex <- rbind(varex, `Proportion Var` = vx/p)
         if (factors > 1)
             varex <- rbind(varex, `Cumulative Var` = cumsum(vx/p))
     }
     cat("\n")
     print(round(varex, digits))
     invisible(x)
}
<environment: namespace:stats>

So vx = colSums(x^2); "SS loadings" = vx, "Proportion Var" = vx/p, and  
`Cumulative Var` = cumsum(vx/p).

You should be able to take it from there, since presumably you can  
work with the x matrix which is really just "load" by another name.

 > x <- load

 > colSums(x^2)
Comp.1 Comp.2 Comp.3 Comp.4
      1      1      1      1


-- 
David Winsemius
>
>
> Can anyone help me ?
>
> Nash 2009.02.07
>
>
>
>
>
> --
> Nash - morrison at ibms.sinica.edu.tw
>
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