# [R] Get the difference between two matrices with different length

Dimitris Rizopoulos dimitris.rizopoulos at med.kuleuven.be
Fri May 4 13:52:59 CEST 2007

```try this:

ind1 <- do.call("paste", c(as.data.frame(mat1[, 1:2]), sep = "\r"))
ind2 <- do.call("paste", c(as.data.frame(mat2[, 1:2]), sep = "\r"))
mat1[ind1 %in% ind2, 3] - mat2[ind2 %in% ind1, 3]

I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
http://www.student.kuleuven.be/~m0390867/dimitris.htm

----- Original Message -----
From: "Felix Wave" <felix-wave at vr-web.de>
To: <r-help at stat.math.ethz.ch>
Sent: Friday, May 04, 2007 1:26 PM
Subject: [R] Get the difference between two matrices with different
length

> Hello,
> I have got two matrices with different length. The matrices have 3
> columuns. The first two are coordinates. The third is a measurement.
>
> Now I want to get a subtraction between every single value of the
> third column (between matrix1 and matrix2), but only if the two
> first coordinates in matrix1 and matrix2 are the same.
>
> I tried "FUN=?" in aggregate and ave, but I don't know the command
> for such a subtraction?
>
>
> Thank's a lot.
> Felix
>
>
> ---------------
>
> The matrixes (examlple):
>
> 1 0.1 0.0042
> 1 0.2 0.00423
> 1 0.4 0.00467
> 1 0.5 0.00518
> 1 0.6 0.0061
>
>
> 1 0.1 0.0043
> 1 0.2 0.00442
> 1 0.3 0.00433
> 1 0.4 0.0045
> 1 0.5 0.00524
> 1 0.7 0.006
>
>
>
> My aim:
> -------
> 1 0.1 -0.0001
> 1 0.2 -0.00019
> 1 0.4 0.00017
> 1 0.5 -0.00006
>
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