# [R] About calculating average values from several matrices

Doran, Harold HDoran at air.org
Tue May 9 17:14:14 CEST 2017

```Im not sure if you’re asking a question or confirming that it works for you. But, obviously, the code below behaves as expected

From: lily li [mailto:chocold12 at gmail.com]
Sent: Tuesday, May 09, 2017 11:13 AM
To: Doran, Harold <HDoran at air.org>
Cc: Charles Determan <cdetermanjr at gmail.com>; R mailing list <r-help at r-project.org>
Subject: Re: [R] About calculating average values from several matrices

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<mailto:HDoran at air.org>> wrote:
?round

From: lily li [mailto:chocold12 at gmail.com<mailto:chocold12 at gmail.com>]
Sent: Tuesday, May 09, 2017 11:10 AM
To: Charles Determan <cdetermanjr at gmail.com<mailto:cdetermanjr at gmail.com>>
Cc: Doran, Harold <HDoran at air.org<mailto:HDoran at air.org>>; R mailing list <r-help at r-project.org<mailto: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<mailto: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<mailto: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<mailto: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<mailto:chocold12 at gmail.com>]
> *Sent:* Tuesday, May 09, 2017 10:44 AM
> *To:* Doran, Harold <HDoran at air.org<mailto:HDoran at air.org>>
> *Cc:* R mailing list <r-help at r-project.org<mailto: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<mailto: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<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<mailto: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]]
>
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