[R] How to index the occasions in a vector repeatedly under condition 1? if not, it will give a new index.

[William Dunlap]

Use cumsum(logicalVector) to increment a counter at the TRUE positions in
logicalVector. .  E.g.,

> d <- c(NA, 0, 0, 0, 8, 0, 577, 69, 0)
> is_true <- function(x) !is.na(x) & x
> 1 + cumsum( is_true(d >= 15) )
[1] 1 1 1 1 1 1 2 3 3

Some packages have the equivalent of that is_true function, which maps
FALSE and NA to FALSE and TRUE to TRUE.  I don't think core R contains such
a function.

Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Wed, Feb 19, 2020 at 7:08 AM Lijun Zhao <lijun.zhao using adelaide.edu.au>
wrote:

> Dear all,
> Could you please help me how to get the output as I described in the
> following example?
>
> x<-c(543,  543,  543,  543,  551 , 551 ,1128 ,1197, 1197)
> diff<-x-lag(x)
> diff
> [1]  NA   0   0   0   8   0 577  69   0
>
> How to index the occasions in x repeatedly if the diff<15? if diff>=15, it
> will give a new index.
> I want the output be like y.
>
> y<-c(1,1,1,1,1,1,2,3,3)
>
> Thank you so much,
>
> Lijun Zhao (PhD Candidate)
> Nutrition and Metabolism
> Level 7 SAHMRI
> North Terrace
> Adelaide 5005
> Ph    : +61 8 8128 4898
> e-mail: lijun.zhao using adelaide.edu.au<mailto:lijun.zhao using adelaide.edu.au> or
> lijun.zhao using sahmri.com<mailto:lijun.zhao using sahmri.com>
>
>
>
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>
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