[R] Odp: Extract rows with non-zero elements
petr.pikal at precheza.cz
Tue May 4 11:21:32 CEST 2010
r-help-bounces at r-project.org napsal dne 04.05.2010 09:50:28:
> Dear all,
> In my dataset I have 12 columns and 5824 rows. The second column
> information about the height of a claim: it might be zero or positive. I
> would like to do an analysis on the positive part of this matrix, but I
> need the other colums with this. So if there are like 1000 rows where
> second column is positive, I would like to extract this 1000x13 matrix
> another matrix.
> The beginning of my code is:
> Cars <- read.csv(filename, header=TRUE, row.names=NULL, sep=";")
Do not do that. you will have troubles with referencing objects and
changing them, unless you perfectly know which object you
> n <- as.numeric(n)
> s <- as.numeric(s)
you either have n and s as numeric than there is no need for as.numeric or
they come aout as factors and in that case you get numerical
***representation*** of levels, which is probably not what you want.
> # et cetera, the other variabeles are declared as numeric or as factors
> # I've tried to extract the data the following way:
> Cars2 <- Cars[Cars$s!=0]
see ?"[" and matrix/data.frame indexing
Cars2 <- Cars[Cars$s!=0, ]
> #However, then I get the error message:
> Error in `[.data.frame`(Cars, Cars$s != 0) : undefined columns selected
> # If I try
> # I do get the positive s-values, but how can I get all colums in a
Cars is ***not*** matrix but data.frame. Seems to be minor difference but
it is like mountain bike and racing bike. They look similar but their use
and properties are quite different.
> Does anyone know how this can be done? Your help would be greatly
> Frank van Berkum
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