Re: [R] How to compare X1 = X2 = ... = Xn?

From: Sundar Dorai-Raj <sundar.dorai-raj_at_pdf.com>
Date: Tue 20 Jul 2004 - 04:03:39 EST

ink2">F Duan wrote:

> Dear All,
>
>
>
> I have a data frame with n columns: X1, X2, ., Xn. Now I want to create a

> new column: if X1 = X2 = . = Xn, the value is 1; Otherwise, the value is 0.
>
>
>

> How to do that in a quick way instead of doing (n choose 2) comparisons?
>
>
>

> Thank you,
>
>
>

> Frank
>
>

How about something like?

x <- data.frame(X1 = c(1, 1, 2, 4),

                 X2 = c(4, 1, 2, 5),
                 X3 = c(2, 1, 2, 2))

nuniq <- function(x) length(unique(x))
as.numeric(apply(as.matrix(x), 1, nuniq) == 1)

--sundar



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