Get the first non zero digit in R similar to Mathematica

Question

In mathematica we have RealDigits that can identify the first non-zero number for both numbers with decimal point and integer values. See below as an example:

RealDigits[ 0.00318, 10, 1]
{{3},-2}
RealDigits[ 419, 10, 1]
{{4},-2}

In the above example the function identifies, 3 and 4 respectively for 0.00318 and 419.

Is there a similar function in R?

take a look at: https://www.r-bloggers.com/2010/04/significant-figures-in-r-and-info-zeros/ — tester, Nov 11 '20 at 21:04
Did you check this threat and solution? https://stackoverflow.com/a/3443955/9783433 Maybe it helps — mischva11, Nov 11 '20 at 21:05

score 4 · Accepted Answer · edited Nov 11 '20 at 21:26

4

You could do:

x <- c(0.0000318, 419)

as.numeric(substr(formatC(x, format = 'e'), 1, 1))
# [1] 3 4

edited Nov 11 '20 at 21:26

zx8754

52,746
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answered Nov 11 '20 at 21:08

Onyambu

67,392
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score 1 · Answer 2 · answered Nov 11 '20 at 21:34

This function will accept vector arguments as well as a depth parameter letting you define how many digits you want to have after the first significant one.

x <- c(0.00318, 0.000489, 895.12)
RealDigits <- function(x, depth=1) {
  y <- as.character(x)
  ysplit <- strsplit(y,"")
  ysplit <- strsplit(y,"")
  last0 <- lapply(ysplit, function(x) tail(which(x==0),1))
  last00 <- sapply(last0, function(x) if (length(x) ==0) 0 else x )
  res <- substr(y, last00+1, as.numeric(sapply(y, nchar)))
  return(substr(res, 0,depth))
}
RealDigits(x)
RealDigits(x, depth =2)

> RealDigits(x)
[1] "3" "4" "8"
> RealDigits(x, depth =2)
[1] "31" "48" "89"

Get the first non zero digit in R similar to Mathematica

2 Answers2