R help - Jun 2025 - Converting dataframe to matrix

On Thu, 26 Jun 2025 03:45:50 +0530
Daniel Lobo <danielobo9976 at gmail.com> wrote:
> Hi,
> 
> I have a dataframe for which all columns are numeric but categorical.
I don't understand what that means.  Perhaps an example?
> There are some missing values as well
> 
> Typically, I have CSV file saved in drive, and then read it using
> read.csv command
Is that relevant?
> Can I use as.matrix(na.omit(<<my dataframe loaded using
read.csv>>))
> to convert such dataframe to matrix?
> 
> I there any data loss or change that may occur if I use as.matrix
> command?
I think your question is too vague for anyone to be able to answer this.
 
> I remember that some experts recommends not to use as.matrix()
> command to convert a dataframe to matrix.
My guess is that the problem is that as.matrix() will coerce all of the
columns of a data frame to a common class, which might yield unexpected
results.
> Any guidance will be very helpful.
It's possible that data.matrix() might be useful.

But basically you should think carefully about what the nature of the
entries of your data frame could possibly be, and then design your code
to accommodate all of these possibilities, throwing an error if any
entry does not conform to any of the possibilities that you envisage.

cheers,

Rolf Turner

-- 
Honorary Research Fellow
Department of Statistics
University of Auckland
Stats. Dep't. (secretaries) phone:
         +64-9-373-7599 ext. 89622
Home phone: +64-9-480-4619

To add to Rolf's comments:

1. What you do with your data may depend on what you want to do with it
*after* you have fiddled with its structure. Treating numerical categories
as numerics is often a bad idea for many kinds of analyses or even graphics;

2. Note that na.omit(d) when d is a data frame or matrix will omit whole
rows containing an NA, which may be disastrous for understanding the story
your data have to tell. Again, it depends on what you actually want to do
with your data, as Rolf intimated.

Caveat: I am *not* an expert

Cheers,
Bert



2.

On Wed, Jun 25, 2025 at 4:57?PM Rolf Turner <rolfturner at posteo.net>
wrote:
>
> On Thu, 26 Jun 2025 03:45:50 +0530
> Daniel Lobo <danielobo9976 at gmail.com> wrote:
>
> > Hi,
> >
> > I have a dataframe for which all columns are numeric but categorical.
>
> I don't understand what that means.  Perhaps an example?
>
> > There are some missing values as well
> >
> > Typically, I have CSV file saved in drive, and then read it using
> > read.csv command
>
> Is that relevant?
>
> > Can I use as.matrix(na.omit(<<my dataframe loaded using
read.csv>>))
> > to convert such dataframe to matrix?
> >
> > I there any data loss or change that may occur if I use as.matrix
> > command?
>
> I think your question is too vague for anyone to be able to answer this.
>
> > I remember that some experts recommends not to use as.matrix()
> > command to convert a dataframe to matrix.
>
> My guess is that the problem is that as.matrix() will coerce all of the
> columns of a data frame to a common class, which might yield unexpected
> results.
>
> > Any guidance will be very helpful.
>
> It's possible that data.matrix() might be useful.
>
> But basically you should think carefully about what the nature of the
> entries of your data frame could possibly be, and then design your code
> to accommodate all of these possibilities, throwing an error if any
> entry does not conform to any of the possibilities that you envisage.
>
> cheers,
>
> Rolf Turner
>
> --
> Honorary Research Fellow
> Department of Statistics
> University of Auckland
> Stats. Dep't. (secretaries) phone:
>          +64-9-373-7599 ext. 89622
> Home phone: +64-9-480-4619
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> https://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
	[[alternative HTML version deleted]]

My data frame looks like below

dat = structure(list(a = c(66, 100, 100, 100, 100, 100, 100, 66, 100,

66), b = c(100, 50, 100, 100, 100, 100, 100, 100, 100, 100),

    c = c(75, 25, 75, 50, 50, 50, 50, 50, 75, 25)), class
"data.frame", row.names = c(NA,

-10L))

The values are basically categories for each column, however there may
be missing values present, which typically represented as NA.

My question is can I directly use as.matrix(na.omit(dat)) to convert
this to matrix?


On Thu, 26 Jun 2025 at 05:27, Rolf Turner <rolfturner at posteo.net>
wrote:
>
>
> On Thu, 26 Jun 2025 03:45:50 +0530
> Daniel Lobo <danielobo9976 at gmail.com> wrote:
>
> > Hi,
> >
> > I have a dataframe for which all columns are numeric but categorical.
>
> I don't understand what that means.  Perhaps an example?
>
> > There are some missing values as well
> >
> > Typically, I have CSV file saved in drive, and then read it using
> > read.csv command
>
> Is that relevant?
>
> > Can I use as.matrix(na.omit(<<my dataframe loaded using
read.csv>>))
> > to convert such dataframe to matrix?
> >
> > I there any data loss or change that may occur if I use as.matrix
> > command?
>
> I think your question is too vague for anyone to be able to answer this.
>
> > I remember that some experts recommends not to use as.matrix()
> > command to convert a dataframe to matrix.
>
> My guess is that the problem is that as.matrix() will coerce all of the
> columns of a data frame to a common class, which might yield unexpected
> results.
>
> > Any guidance will be very helpful.
>
> It's possible that data.matrix() might be useful.
>
> But basically you should think carefully about what the nature of the
> entries of your data frame could possibly be, and then design your code
> to accommodate all of these possibilities, throwing an error if any
> entry does not conform to any of the possibilities that you envisage.
>
> cheers,
>
> Rolf Turner
>
> --
> Honorary Research Fellow
> Department of Statistics
> University of Auckland
> Stats. Dep't. (secretaries) phone:
>          +64-9-373-7599 ext. 89622
> Home phone: +64-9-480-4619
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
https://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.