[R] selecting columns from a data frame or data table by type, ie, numeric, integer

[William Dunlap]

> dt1[ vapply(dt1, FUN=is.numeric, FUN.VALUE=NA) ]
    a   c
1   1 1.1
2   2 1.0
...
10 10 0.2



Bill Dunlap
TIBCO Software
wdunlap tibco.com

On Fri, Apr 29, 2016 at 9:19 AM, Carl Sutton via R-help <
r-help at r-project.org> wrote:

> Good morning RGuru's
> I have a data frame of 575 columns.  I want to extract only those columns
> that are numeric(double) or integer to do some machine learning with.  I
> have searched the web for a couple of days (off and on) and have not found
> anything that shows how to do this.   Lots of ways to extract rows, but not
> columns.  I have attempted to use "(x == y)" indices extraction method but
> that threw error that == was for atomic vectors and lists, and I was doing
> this on a data frame.
>
> My test code is below
>
> #  a technique to get column classes
> library(data.table)
> a <- 1:10
> b <- c("a","b","c","d","e","f","g","h","i","j")
> c <- seq(1.1, .2, length = 10)
> dt1 <- data.table(a,b,c)
> str(dt1)
> col.classes <- sapply(dt1, class)
> head(col.classes)
> dt2 <- subset(dt1, typeof = "double" | "numeric")
> str(dt2)
> dt2   #  not subset
> dt2 <- dt1[, list(typeof = "double")]
> str(dt2)
> class_data <- dt1[,sapply(dt1,is.integer) | sapply(dt1, is.numeric)]
> class_data
> sum(class_data)
> typeof(class_data)
> names(class_data)
> str(class_data)
>  Any help is appreciated
> Carl Sutton CPA
>
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>
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