[R] Problems with data structure when using plsr() from package pls

Sarah Goslee sarah.goslee at gmail.com
Fri Jan 15 13:55:52 CET 2016

Backing up a step:

On Wednesday, January 13, 2016, CG Pettersson <cg.pettersson at lantmannen.com>

> R version 3.2.3, W7 64bit.
> Dear all!
> I am trying to make pls-regression using plsr() from package pls, with
> Mevik & Wehrens (2007) as tutorial and the datasets from the package.
> Everything works real nice as long as I use the supplied datasets, but I
> don´t understand how to prepare my own data.
> This is what I have done:
> > frame1 <- data.frame(gushVM, I(n96))

Which ISN'T what the example you're following did. You didn't name the

frame1 <- data.frame(gushVM, n96 = I(n96))

so R can't find anything named n96 within frame1 because it's probably
named some variant on I(n96).

str(frame1) would have told you this.


> Where gushVM is a vector with fifteen reference analysis values of a
> quality problem in grain and n96 is a matrix with fifteen rows and 96
> columns from an electronic nose. I try to copy the methods as in 3.2 in
> Mevik & Wehrens, and want to keep n96 as one variable to avoid addressing
> 96 different variables in the plsr call. If I don´t use I() in the call I
> get 96 variables instead.
> Looking at the dataframe by summary(frame1) get a return quite like
> summary(gasoline) from the package (not shown here).
> But when I try to use plsr() with my own data it doesn´t work due to an
> error in the data structure:
> > pls1 <- plsr(gushVM ~ n96, data = frame1)
> Error in model.frame.default(formula = gushVM ~ n96, data = frame1) :
>   invalid type (list) for variable 'n96'
> >
> So, n96 has turned into a list, and that is a problem. If gushVM is a
> vector (one variable) och a matrix (five variables) does not seem to change
> anything, managing n96 is the problem
> I have tried all alternative ways of creating a proper data frame
> suggested in the article with exactly the same result.
> I have tried the documentation for data.frame() but I probably don´t
> understand what it says.
> What should I do to change "n96" into something better than "list"?
> Thanks
> /CG
> Med vänlig hälsning/Best regards
> CG Pettersson
> Scientific Project Manager, PhD
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Sarah Goslee

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