# [R] About calculating average values from several matrices

lily li chocold12 at gmail.com
Tue May 9 17:12:59 CEST 2017

```Yes, that means to control decimal numbers. For example, use round(2.3122,
digits=1), it gets 2.3

On Tue, May 9, 2017 at 9:11 AM, Doran, Harold <HDoran at air.org> wrote:

> ?round
>
>
>
>
>
> *From:* lily li [mailto:chocold12 at gmail.com]
> *Sent:* Tuesday, May 09, 2017 11:10 AM
> *To:* Charles Determan <cdetermanjr at gmail.com>
> *Cc:* Doran, Harold <HDoran at air.org>; R mailing list <r-help at r-project.org
> >
> *Subject:* Re: [R] About calculating average values from several matrices
>
>
>
> Thanks very much, it works. But how to round the values to have only 1
> decimal digit or 2 decimal digits? I think by dividing, the values are
> double type now. Thanks again.
>
>
>
>
>
> On Tue, May 9, 2017 at 9:04 AM, Charles Determan <cdetermanjr at gmail.com>
> wrote:
>
> If you want the mean of each element across you list of matrices the
> following should provide what you are looking for where Reduce sums all
> your matrix elements across matrices and the simply divided my the number
> of matrices for the element-wise mean.
>
> Reduce(`+`, mylist)/length(mylist)
>
> Regards,
>
> Charles
>
>
>
> On Tue, May 9, 2017 at 9:52 AM, lily li <chocold12 at gmail.com> wrote:
>
> I meant for each cell, it takes the average from other dataframes at the
> same cell. I don't know how to deal with row names and col names though, so
> it has the error message.
>
> On Tue, May 9, 2017 at 8:50 AM, Doran, Harold <HDoran at air.org> wrote:
>
> > It’s not clear to me what your actual structure is. Can you provide
> > str(object)? Assuming it is a list, and you want the mean over all cells
> or
> > columns, you might want like this:
> >
> >
> >
> > myData <- vector("list", 3)
> >
> >
> >
> > for(i in 1:3){
> >
> >                 myData[[i]] <- matrix(rnorm(100), 10, 10)
> >
> >                 }
> >
> >
> >
> > ### mean over all cells
> >
> > sapply(myData, function(x) mean(x))
> >
> >
> >
> > ### mean over all columns
> >
> > sapply(myData, function(x) colMeans(x))
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > *From:* lily li [mailto:chocold12 at gmail.com]
> > *Sent:* Tuesday, May 09, 2017 10:44 AM
> > *To:* Doran, Harold <HDoran at air.org>
> > *Cc:* R mailing list <r-help at r-project.org>
> > *Subject:* Re: [R] About calculating average values from several matrices
>
>
> >
> >
> >
> > I'm trying to get a new dataframe or whatever to call, which has the same
> > structure with each file as listed above. For each cell in the new
> > dataframe or the new file, it is the average value from former dataframes
> > at the same location. Thanks.
> >
> >
> >
> > On Tue, May 9, 2017 at 8:41 AM, Doran, Harold <HDoran at air.org> wrote:
> >
> > Are you trying to take the mean over all cells, or over rows/columns
> > within each dataframe. Also, are these different dataframes stored
> within a
> > list or are they standalone?
> >
> >
> >
> >
> > -----Original Message-----
> > From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of lily li
> > Sent: Tuesday, May 09, 2017 10:39 AM
> > To: R mailing list <r-help at r-project.org>
>
> > Subject: [R] About calculating average values from several matrices
> >
> > Hi R users,
> >
> > I have a question about manipulating the data.
> > For example, there are several such data frames or matrices, and I want
> to
> > calculate the average value from all the data frames or matrices. How to
> do
> > it? Also, should I convert them to data frame or matrix first? Right now,
> > when I use typeof() function, each one is a list.
> >
> > file1
> >             jan   feb   mar   apr   may   jun   jul   aug   sep   oct
>  nov
> >
> > app1   1.1   1.2    0.8    0.9   1.3    1.5   2.2   3.2   3.0    1.2
>  1.1
> > app2   3.1   3.2    2.8    2.5   2.3    2.5   3.2   3.0   2.9    1.8
>  1.8
> > app3   5.1   5.2    3.8    4.9   5.3    5.5   5.2   4.2   5.0    4.2
>  4.1
> >
> > file2
> >             jan   feb   mar   apr   may   jun   jul   aug   sep   oct
>  nov
> >
> > app1   1.9   1.5    0.5    0.9   1.2    1.8   2.5   3.7   3.2    1.5
>  1.6
> > app2   3.5   3.7    2.3    2.2   2.5    2.0   3.6   3.2   2.8    1.2
>  1.4
> > app3   5.5   5.0    3.5    4.4   5.4    5.6   5.3   4.4   5.2    4.3
>  4.2
> >
> > file3 has the similar structure and values...
> >
> > There are eight such files, and when I use the function mean(file1,
> file2,
> > file3, ..., file8), it returns the error below. Thanks for your help.
> >
> > Warning message:
> > In mean.default(file1, file2, file3, file4, file5, file6, file7,  :
> >   argument is not numeric or logical: returning NA
> >
> >         [[alternative HTML version deleted]]
> >
> > ______________________________________________
>
> > 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 http://www.R-project.org/
> > posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
> >
> >
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> 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 http://www.R-project.org/
> posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
>
>
>
>

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