Message-ID: <1363212310.13129.YahooMailNeo@web142605.mail.bf1.yahoo.com>
Date: 2013-03-13T22:05:10Z
From: arun
Subject: calculating column difference in a matrix
In-Reply-To: <CAEd7G2eTOoB0DtNUtWi4ZKqPFwJAGB6gJ_WDjH9FB1=Y9eZ+wg@mail.gmail.com>
Hi,
Try this:
a1<-a
a1[rowSums(is.na(a1))==1][ is.na(a1[rowSums(is.na(a1))==1])]<-0
library(matrixStats)?c1<- cbind(a,rowDiffs(a1))
?c1
#???? [,1] [,2] [,3]
#[1,]??? 2??? 5??? 3
#[2,]??? 3??? 8??? 5
#[3,]??? 4?? NA?? -4
#[4,]?? NA??? 8??? 8
#[5,]?? NA?? NA?? NA
identical(c,c1)
#[1] TRUE
A.K.
----- Original Message -----
From: Pedro Mardones <mardones.p at gmail.com>
To: R-help at r-project.org
Cc:
Sent: Wednesday, March 13, 2013 5:43 PM
Subject: [R] calculating column difference in a matrix
Dear R users;
Consider the following toy example:
a <- matrix(c(2,3,4,NA,NA,5,8,NA,8,NA), 5, 2)
b <- cbind(a,apply(a, 1, diff, na.rm = TRUE))
What I would like be able to get is:
c <- matrix(c(2,3,4,NA,NA,5,8,NA,8,NA,3,5,-4,8,NA), 5, 3)
i.e., for each row if both values (column 1 and 2) are NA then the
difference must return NA, but if any of those two values is different
from NA (!is.na), I would like to actually perform the difference
(something like assigning 0 instead to NA to the cell).
I'd appreciate any hint or comment
Best,
Pedro
BTW: the reason of this is that I'm trying to build an error checking
procedure for a big dataset I have
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