[R] Compare two subsequent rows based on specific values of a string

[Michel]

Thanks I'm lookin for yur example

-----Message d'origine-----
De : r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] De
la part de arun
Envoyé : vendredi 20 septembre 2013 18:11
À : R help
Objet : Re: [R] Compare two subsequent rows based on specific values of a
string

Hi,
May be this helps:
dat1<- read.table(text="x1    x2    x3   x4
1     xz   ab    cd    ef
2     ab   fz    cd    ef
3     ab   cd   dy    dx",sep="",header=TRUE,stringsAsFactors=FALSE)
dat1$changes_to_row_above<- sapply(seq_len(nrow(dat1)),function(i)
{x1<-dat1[,i]%in% dat1[,i-1];if(any(x1)) sum(x1,na.rm=TRUE) else NA})
 dat1
#  x1 x2 x3 x4 changes_to_row_above
#1 xz ab cd ef                   NA
#2 ab fz cd ef                    1
#3 ab cd dy dx                    2

A.K.



Dear all, 

I would like to compare two rows and check whether something changed. The
only thing is, it is not always the same column that needs to be compared.
It is rather a matrix of values. The outcome would be a number of changes in
these, for instance: "of row 2, there are 3 exactly  same values in row 3".
I will make up an example: 

      x1    x2    x3   x4   changes_to_row_above
1     xz   ab    cd    ef   NA
2     ab   fz    cd    ef   1
3     ab   cd   dy    dx   2
and so forth... 

Do you think that would be possible? Is there an easy function to do so? It
would be great help guys, thanks a lot in advance, sorry for my bad data
manipulation knowledge... 

Tobi

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